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• help: cannot make ubuntu 64-bit v12.04 install work

  - by honestann

  I decided it was time to update my ubuntu (single boot) computer from 64-bit v10.04 to 64-bit v12.04. Unfortunately, for some reason (or reasons) I just can't make it work. Note that I am attempting a fresh install of 64-bit v12.04 onto a new 3TB hard disk, not an upgrade of the 1TB hard disk that has contained my 64-bit v10.04 installation. To perform the attempted install of v12.04 I unplug the SATA cable from the 1TB drive and plug it into the 3TB drive (to avoid risking damage to my working v10.04 installation). I downloaded the ubuntu 64-bit v12.04 install DVD ISO file (~1.6 GB) from the ubuntu releases webpage and burned it onto a DVD. I have downloaded the DVD ISO file 3 times and burned 3 of these installation DVDs (twice with v10.04 and once with my winxp64 system), but none of them work. I run the "check disk" on the DVDs at the beginning of the installation process to assure the DVD is valid. I also tried to install on two older 250GB seagate drives in the same computer. During every attempt I plug the same SATA cable (sda) into only one disk drive (the 3TB or one of the 250GB drives) and leave the other disk drives unconnected (for simplicity). Installation takes about 30 minutes on the 250GB drives, and about 60 minutes on the 3TB drive - not sure why. When I install on the 250GB drives, the install process finishes, the computer reboots (after the install DVD is removed), but I get a grub error 15. It is my understanding that 64-bit ubuntu (and 64-bit linux in general) has no problem with 3TB disk drives. In the BIOS I have tried having EFI set to "enabled" and "auto" with no apparent difference (no success). I have tried partitioning the drive in a few ways to see if that makes a difference, but so far it has not mattered. Typically I manually create partitions something like this: 8GB swap 8GB /boot ext4 3TB / ext4 But I've also tried the following, just in case it matters: 100MB boot efi 8GB swap 8GB /boot ext4 3TB / ext4 Note: In the partition dialog I specify bootup on the same drive I am partitioning and installing ubuntu v12.04 onto. It is a VERY DANGEROUS FACT that the default for this always comes up with the wrong drive (some other drive, generally the external drive). Unless I'm stupid or misunderstanding something, this is very wrong and very dangerous default behavior. Note: If I connect the SATA cable to the 1TB drive that has been my ubuntu 64-bit v10.04 system drive for the past 2 years, it boots up and runs fine. I guess there must be a log file somewhere, and maybe it gives some hints as to what the problem is. I should be able to boot off the 1TB drive with the 3TB drive connected as a secondary (non-boot) drive and get the log file, assuming there is one and someone tells me the name (and where to find it if the name is very generic). After installation on the 3TB drive completes and the system reboots, the following prints out on a black screen: Loading Operating System ... Boot from CD/DVD : Boot from CD/DVD : error: unknown filesystem grub rescue Note: I have two DVD burners in the system, hence the duplicate line above. The same install and reboot on the 250GB drives generates "grub error 15". Sigh. Any ideas? ========== motherboard == gigabyte 990FXA-UD7 CPU == AMD FX-8150 8-core bulldozer @ 3.6 GHz RAM == 8GB of DDR3 in 2 sticks (matched pair) HDD == seagate 3TB SATA3 @ 7200 rpm (new install 64-bit v12.04) HDD == seagate 1TB SATA3 @ 7200 rpm (current install 64-bit v10.04) GPU == nvidia GTX-285 ??? == no overclocking or other funky business USB == external seagate 2TB HDD for making backups DVD == one bluray burner (SATA) DVD == one DVD burner (SATA) The current ubuntu 64-bit v10.04 system boots and runs fine on a seagate 1TB.

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• Access Denied

  - by Tony Davis

  When Microsoft executives wake up in the night screaming, I suspect they are having a nightmare about their own version of Frankenstein's monster. Created with the best of intentions, without thinking too hard of the long-term strategy, and having long outlived its usefulness, the monster still lives on, occasionally wreaking vengeance on the innocent. Its name is Access; a living synthesis of disparate body parts that is resistant to all attempts at a mercy-killing. In 1986, Microsoft had no database products, and needed one for their new OS/2 operating system, the successor to MSDOS. In 1986, they bought exclusive rights to Sybase DataServer, and were also intent on developing a desktop database to capture Ashton-Tate's dominance of that market, with dbase. This project, first called 'Omega' and later 'Cirrus', eventually spawned two products: Visual Basic in 1991 and Access in late 1992. Whereas Visual Basic battled with PowerBuilder for dominance in the client-server market, Access easily won the desktop database battle, with Dbase III and DataEase falling away. Access did an excellent job of abstracting and simplifying the task of building small database applications in a short amount of time, for a small number of departmental users, and often for a transient requirement. There is an excellent front end and forms generator. We not only see it in Access but parts of it also reappear in SSMS. It's good. A business user can pull together useful reports, without relying on extensive technical support. A skilled Access programmer can deliver a fairly sophisticated application, whilst the traditional client-server programmer is still sharpening his pencil. Even for the SQL Server programmer, the forms generator of Access is useful for sketching out application designs. So far, so good, but here's where the problems start; Access ties together two different products and the backend of Access is the bugbear. The limitations of Jet/ACE are well-known and documented. They range from MDB files that are prone to corruption, especially as they grow in size, pathetic security, and "copy and paste" Backups. The biggest problem though, was an infamous lack of scalability. Because Microsoft never realized how long the product would last, they put little energy into improving the beast. Microsoft 'ate their own dog food' by using Access for Microsoft Exchange and Outlook. They choked on it. For years, scalability and performance problems with Exchange Server have been laid at the door of the Jet Blue engine on which it relies. Substantial development work in Exchange 2010 was required, just in order to improve the engine and storage schema so that it more efficiently handled the reading and writing of mails. The alternative of using SQL Server just never panned out. The Jet engine was designed to limit concurrent users to a small number (10-20). When Access applications outgrew this, bitter experience proved that there really is no easy upgrade path from Access to SQL Server, beyond rewriting the whole lot from scratch. The various initiatives to do this never quite bridged the cultural gulf between Access and a true relational database So, what are the obvious alternatives for small, strategic database applications? I know many users who, for simple 'list maintenance' requirements are very happy using Excel databases. Surely, now that PowerPivot has led the way, it is time for Microsoft to offer a new RAD package for database application development; namely an Excel-based front end for SQL Server Express. In that way, we'll have a powerful and familiar front end, to a scalable database, and a clear upgrade path when an app takes off and needs to go enterprise. Cheers, Tony.

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• Performing an upgrade from TFS 2008 to TFS 2010

  - by Enrique Lima

  I recently had to go through the process of migrating a TFS 2008 SP1 to a TFS 2010 environment. I will go into the details of the tasks that I went through, but first I want to explain why I define it as a migration and not an upgrade. When this environment was setup, based on support and limitations for TFS 2008, we used a 32 bit platform for the TFS Application Tier and Build Servers.  The Data Tier, since we were installing SP1 for TFS 2008, was done as a 64 bit installation.  We knew at that point that TFS 2010 was in the picture so that served as further motivation to make that a 64bit install of SQL Server.  The SQL Server at that point was a single instance (Default) installation too.  We had a pretty good strategy in place for backups of the databases supporting the environment (and this made the migration so much smoother), so we were pretty familiar with the databases and the purpose they serve. I am sure many of you that have gone through a TFS 2008 installation have encountered challenges and trials.  And likely even more so if you, like me, needed to configure your deployment for SSL.  So, frankly I was a little concerned about the process of migrating.  They say practice makes perfect, and this environment I worked on is in some way my brain child, so I was not ready nor willing for this to be a failure or something that would impact my client’s work. Prior to going through the migration process, we did the install of the environment.  The Data Tier was the same, with a new Named instance in place to host the 2010 install.  The Application Tier was in place too, and we did the DefaultCollection configuration to test and validate all components were in place as they should. Anyway, on to the tasks for the migration (thanks to Martin Hinselwood for his very thorough documentation): Close access to TFS 2008, you want to make sure all code is checked in and ready to go.  We stated a difference of 8 hours between code lock and the start of migration to give time for any unexpected delay.  How do we close access?  Stop IIS. Backup your databases.  Which ones? TfsActivityLogging TfsBuild TfsIntegration TfsVersionControl TfsWorkItemTracking TfsWorkItemTrackingAttachments Restore the databases to the new Named Instance (make sure you keep the same names) Now comes the fun part! The actual import/migration of the databases.  A couple of things happen here. The TfsIntegration database will be scanned, the other databases will be checked to validate they exist.  Those databases will go through a process of data being extracted and transferred to the TfsVersionControl database to then be renamed to Tfs_<Collection>. You will be using a tool called tfsconfig and the option import. This tool is located in the TFS 2010 installation path (C:\Program Files\Microsoft Team Foundation Server 2010\Tools),  the command to use is as follows:    tfsconfig import /sqlinstance:<instance> /collectionName:<name> /confirmed Where <instance> is going to be the SQL Server instance where you restored the databases to.  <name> is the name you will give the collection. And to explain /confirmed, well this means you have done a backup of the databases, why?  well remember you are going to merge the databases you restored when you execute the tfsconfig import command. The process will go through about 200 tasks, once it completes go to Team Foundation Server Administration Console and validate your imported databases and contents. We’ll keep this manageable, so the next post is about how to complete that implementation with the SSL configuration.

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• What Counts For a DBA – Decisions

  - by Louis Davidson

  It’s Friday afternoon, and the lead DBA, a very talented guy, is getting ready to head out for two well-earned weeks of vacation, with his family, when this error message pops up in his inbox: Msg 211, Level 23, State 51, Line 1. Possible schema corruption. Run DBCC CHECKCATALOG. His heart sinks. It’s ten…no eight…minutes till it’s time to walk out the door. He glances around at his coworkers, competent to handle many problems, but probably not up to the challenge of fixing possible database corruption. What does he do? After a few agonizing moments of indecision, he clicks shut his laptop. He’ll just wait and see. It was unlikely to come to anything; after all, it did say “possible” schema corruption, not definite. In that moment, his fate was sealed. The start of the solution to the problem (run DBCC CHECKCATALOG) had been right there in the error message. Had he done this, or at least took two of those eight minutes to delegate the task to a coworker, then he wouldn’t have ended up spending two-thirds of an idyllic vacation (for the rest of the family, at least) dealing with a problem that got consistently worse as the weekend progressed until the entire system was down. When I told this story to a friend of mine, an opera fan, he smiled and said it described the basic plotline of almost every opera or ‘Greek Tragedy’ ever written. The particular joy in opera, he told me, isn’t the warbly voiced leading ladies, or the plump middle-aged romantic leads, or even the music. No, what packs the opera houses in Italy is the drama of characters who, by the very nature of their life-experiences and emotional baggage, make all sorts of bad choices when faced with ordinary decisions, and so move inexorably to their fate. The audience is gripped by the spectacle of exotic characters doomed by their inability to see the obvious. I confess, my personal experience with opera is limited to Bugs Bunny in “What’s Opera, Doc?” (Elmer Fudd is a great example of a bad decision maker, if ever one existed), but I was struck by my friend’s analogy. If all the DBA cubicles were a stage, I think we would hear many similarly tragic tales, played out to music: “Error handling? We write our code to never experience errors, so nah…“ “Backups failed today, but it’s okay, we’ll back up tomorrow (we’ll back up tomorrow)“ And similarly, they would leave their audience gasping, not necessarily at the beauty of the music, or poetry of the lyrics, but at the inevitable, grisly fate of the protagonists. If you choose not to use proper error handling, or if you choose to skip a backup because, hey, you haven’t had a server crash in 10 years, then inevitably, in that moment you expected to be enjoying a vacation, or a football game, with your family and friends, you will instead be sitting in front of a computer screen, paying for your poor choices. Tragedies are very much part of IT. Most of a DBA’s day to day work has limited potential to wreak havoc; paperwork, timesheets, random anonymous threats to developers, routine maintenance and whatnot. However, just occasionally, you, as a DBA, will face one of those decisions that really matter, and which has the possibility to greatly affect your future and the future of your user’s data. Make those decisions count, and you’ll avoid the tragic fate of many an operatic hero or villain.

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• SQL SERVER – BACKUPIO, BACKUPBUFFER – Wait Type – Day 14 of 28

  - by pinaldave

  Backup is the most important task for any database admin. Your data is at risk if you are not performing database backup. Honestly, I have seen many DBAs who know how to take backups but do not know how to restore it. (Sigh!) In this blog post we are going to discuss about one of my real experiences with one of my clients – BACKUPIO. When I started to deal with it, I really had no idea how to fix the issue. However, after fixing it at two places, I think I know why this is happening but at the same time, I am not sure the fix is the best solution. The reality is that the fix is not a solution but a workaround (which is not optimal, but get your things done). From Book On-Line: BACKUPIO Occurs when a backup task is waiting for data, or is waiting for a buffer in which to store data. This type is not typical, except when a task is waiting for a tape mount. BACKUPBUFFER Occurs when a backup task is waiting for data, or is waiting for a buffer in which to store data. This type is not typical, except when a task is waiting for a tape mount. BACKUPIO and BACKUPBUFFER Explanation: This wait stats will occur when you are taking the backup on the tape or any other extremely slow backup system. Reducing BACKUPIO and BACKUPBUFFER wait: In my recent consultancy, backup on tape was very slow probably because the tape system was very old. During the time when I explained this wait type reason in the consultancy, the owners immediately decided to replace the tape drive with an alternate system. They had a small SAN enclosure not being used on side, which they decided to re-purpose. After a week, I had received an email from their DBA, saying that the wait stats have reduced drastically. At another location, my client was using a third party tool (please don’t ask me the name of the tool) to take backup. This tool was compressing the backup along with taking backup. I have had a very good experience with this tool almost all the time except this one sparse experience. When I tried to take backup using the native SQL Server compressed backup, there was a very small value on this wait type and the backup was much faster. However, when I attempted with the third party backup tool, this value was very high again and was taking much more time. The third party tool had many other features but the client was not using these features. We end up using the native SQL Server Compressed backup and it worked very well. If I get to see this higher in my future consultancy, I will try to understand this wait type much more in detail and so probably I would able to come to some solid solution. Read all the post in the Wait Types and Queue series. Note: The information presented here is from my experience and there is no way that I claim it to be accurate. I suggest reading Book OnLine for further clarification. All the discussion of Wait Stats in this blog is generic and varies from system to system. It is recommended that you test this on a development server before implementing it to a production server. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, SQL Wait Stats, SQL Wait Types, T SQL, Technology

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• Visual Studio 2012 and .NET 4.5 now Live!

  - by Tarun Arora

  Today was the formal launch event for Visual Studio 2012 and .NET 4.5, a state-of-the-art development solution for building modern applications that span connected devices and continuous services, from the client to the cloud. The event was streamed live from http://visualstudiolaunch.com, S.Somasegar corporate vice president of the Developer Division opened the key note, Jason Zander dived deeper into how to leverage Visual Studio 2012 and .NET 4.5 to build modern application. Brian Harry all the awesome features in Visual Studio 2012 to improve the application lifecycle management.   I. Summary of the announcements made today 1. Visual Studio Updates coming this fall –  VS Update will better support agile teams, enable continuous quality, elevate SharePoint development with application lifecycle management (ALM) tools, and expand Visual Studio 2012 Windows development capabilities. It will be available as a community technology preview (CTP) later this month and in final release later this calendar year. A comprehensive list of what will be on offer can be found here. 2. Visual Studio Express 2012 for Windows Desktop – Visual Studio Express 2012 for Windows Desktop brings the newest desktop development capabilities in Visual Studio 2012 to Express users, too. You would be excited to know that the express SKU will support Integration with TFS among some of the other cool features I would like to mention Unit Testing, Unit Testing, Code Analysis, dependency management with NuGet a full list and download links can be found here. 3. F# tools for Visual Studio Express 2012 for web –  This F# Tools release adds in F# 3.0 components, such as the F# 3.0 compiler, F# Interactive, IDE support, and new F# features such as type providers and query expressions to your Visual Studio 2012 express for web. More details and download links can be found here. 4. Visual Studio TFS 2012 Power Tools – The TFS 2012 Power tools brings the goodness of Best Practice Analyzer, Process Template Editor, Storyboard Shapes, Team Explorer enhancements, TFPT command line, TFS Server Backups, etc via to your TFS 2012 installation. It can be downloaded right away from here. II. Road shows There will be many more community road shows this month packaged with hours of demos and discussions. The Visual Studio UK Team has just announced that there will be four UK launch events, face to face session including a product group speaker and partner sessions: Edinburgh, 1st October Manchester, 3rd October London, 4th October Reading, 5th October III. Get Started Download Visual Studio 2012 and the additional supporting software's from here. The Visual Studio development team has put together over 60 videos to help you learn about the new Visual Studio 2012 capabilities in more detail, and all of these will be available for watching here. IV. What’s Next A lot more exciting stuff lined up… Windows 8 Anticipated release: Oct. 26 (UPDATED 9/12) Windows Server 2012 Released (UPDATED 9/4) System Center 2012 Released (UPDATED 9/11) SQL Server 2012 Released (UPDATED 4/2) Internet Explorer 10 Anticipated release: Between Q3 2012 and early 2013 (UPDATED 5/3   Office 2013 Anticipated release: Q4 2012 or Q1 2013(UPDATED 9/12) Exchange 2013 Anticipated release: Q4 2012 (UPDATED 7/26) Visual Studio 2012 Released (UPDATED 9/12) Kinect for Windows Released (UPDATED 9/4) Windows Phone "Tango" and 8 "Tango": Released; Anticipated "Windows Phone 8" release: Q4 2012 (UPDATED 9/5) Dynamics ERP Online Anticipated release: September or October 2012 (UPDATED 7/20) Office 365 Anticipated update schedule: "Almost weekly"(UPDATED 9/12) Windows Azure Rumored CTP release: Spring 2012 (UPDATED 9/7) SharePoint 2013 Anticipated release: Q4 2012 (UPDATED 8/21) Enjoy

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• Protecting Consolidated Data on Engineered Systems

  - by Steve Enevold

  In this time of reduced budgets and cost cutting measures in Federal, State and Local governments, the requirement to provide services continues to grow. Many agencies are looking at consolidating their infrastructure to reduce cost and meet budget goals. Oracle's engineered systems are ideal platforms for accomplishing these goals. These systems provide unparalleled performance that is ideal for running applications and databases that traditionally run on separate dedicated environments. However, putting multiple critical applications and databases in a single architecture makes security more critical. You are putting a concentrated set of sensitive data on a single system, making it a more tempting target.  The environments were previously separated by iron so now you need to provide assurance that one group, department, or application's information is not visible to other personnel or applications resident in the Exadata system. Administration of the environments requires formal separation of duties so an administrator of one application environment cannot view or negatively impact others. Also, these systems need to be in protected environments just like other critical production servers. They should be in a data center protected by physical controls, network firewalls, intrusion detection and prevention, etc Exadata also provides unique security benefits, including a reducing attack surface by minimizing packages and services to only those required. In addition to reducing the possible system areas someone may attempt to infiltrate, Exadata has the following features: 1.    Infiniband, which functions as a secure private backplane 2.    IPTables  to perform stateful packet inspection for all nodes               Cellwall implements firewall services on each cell using IPTables 3.    Hardware accelerated encryption for data at rest on storage cells Oracle is uniquely positioned to provide the security necessary for implementing Exadata because security has been a core focus since the company's beginning. In addition to the security capabilities inherent in Exadata, Oracle security products are all certified to run in an Exadata environment. Database Vault Oracle Database Vault helps organizations increase the security of existing applications and address regulatory mandates that call for separation-of-duties, least privilege and other preventive controls to ensure data integrity and data privacy. Oracle Database Vault proactively protects application data stored in the Oracle database from being accessed by privileged database users. A unique feature of Database Vault is the ability to segregate administrative tasks including when a command can be executed, or that the DBA can manage the health of the database and objects, but may not see the data Advanced Security  helps organizations comply with privacy and regulatory mandates by transparently encrypting all application data or specific sensitive columns, such as credit cards, social security numbers, or personally identifiable information (PII). By encrypting data at rest and whenever it leaves the database over the network or via backups, Oracle Advanced Security provides the most cost-effective solution for comprehensive data protection. Label Security  is a powerful and easy-to-use tool for classifying data and mediating access to data based on its classification. Designed to meet public-sector requirements for multi-level security and mandatory access control, Oracle Label Security provides a flexible framework that both government and commercial entities worldwide can use to manage access to data on a "need to know" basis in order to protect data privacy and achieve regulatory compliance  Data Masking reduces the threat of someone in the development org taking data that has been copied from production to the development environment for testing, upgrades, etc by irreversibly replacing the original sensitive data with fictitious data so that production data can be shared safely with IT developers or offshore business partners  Audit Vault and Database Firewall Oracle Audit Vault and Database Firewall serves as a critical detective and preventive control across multiple operating systems and database platforms to protect against the abuse of legitimate access to databases responsible for almost all data breaches and cyber attacks.  Consolidation, cost-savings, and performance can now be achieved without sacrificing security. The combination of built in protection and Oracle’s industry-leading data protection solutions make Exadata an ideal platform for Federal, State, and local governments and agencies.

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• My collection of favourite TFS utilities

  - by Aaron Kowall

  So, you’re in charge of your company or team’s Team Foundation Server.  Wish it was easier to manage, administer, extend?  Well, here are a few utilities that I highly recommend looking at. I’ve recently had need to rebuild my laptop and upgrade my local TFS environment to TFS 2012 Update 1.  This gave me cause to enumerate some of the utilities I like to have on hand. One of the reasons I love to use TFS on projects is that it’s basically a complete ALM toolkit.  Everything from Task Management, Version Control, Build Management, Test Management, Metrics and Reporting are all there ‘in the box’.  However, no matter how complete a product set it, there are always ways to make it better.  Here are a list of utilities and libraries that are pretty generally useful.  this is not intended to be an exhaustive list of TFS extensions but rather a set that I recommend you look at.  There are many more out there that may be applicable in one scenario or another.  This set of tools should work with TFS 2012 or 2010 if you grab the right version. Most of these tools (and more) are available from the Visual Studio Gallery or CodePlex. General TFS Power Tools – This is ‘the’ collection of utilities and extensions delivered by the Product Group.  Highly recommended from here are the Best Practice Analyzer for ensuring your TFS implementation is healthy and the Team Foundation Server Backups to ensure your TFS databases are backed up correctly. TFS Administrators Toolkit – helps make updates to work item types and reports across many team projects.  Also provides visibility of disk usage by finding large files in version control or test attachments to assist in managing storage utilization. Version Control Git-TF - a set of cross-platform, command line tools that facilitate sharing of changes between TFS and Git. These tools allow a developer to use a local Git repository, and configure it to share changes with a TFS server.  Great for all Git lovers who must integrate into a TFS repository. Testing TFS 2012 Tester Power Tool – A utility for bulk copying test cases which assists in an approach for managing test cases across multiple releases.  A little plug that this utility was written and maintained by Anna Russo of Imaginet where I also work. Test Scribe - A documentation power tool designed to construct documents directly from the TFS for test plan and test run artifacts for the purpose of discussion, reporting etc. Reporting Community TFS Report Extensions - a single repository of SQL Server Reporting Services report for Team Foundation 2010 (and above).  Check out the Test Plan Status report by Imaginet’s Steve St. Jean.  Very valuable for your test managers. Builds TFS Build Manager – A great utility if you are build manager over a complex build environment with many TFS build definitions. Community TFS Build Extensions – contains many custom build activities.  Current release binaries are for TFS 2010 but many of the activities can be recompiled for use with TFS 2012. While compiling this list, I was surprised by the number of TFS utilities and extensions I no longer use/need in TFS 2012 because of the great work by the TFS team addressing many gaps since the 2010 release. Are there any utilities you depend on that I’ve missed?  I’d love to hear about them in the comments!

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• Virtualized data centre&ndash;Part three: Architecture

  - by marc dekeyser

  Having the basics (like discussed in the previous articles) is all good and well, but how do we get started on this?! It can be quite daunting after all!   From my own point of view I can absolutely confirm your worries and concerns, but also tell you that it is not as hard as it seems! Deciding on what kind of motherboard to buy, processor and how much memory is an activity you will spend quite some time doing research on. And that is not even mentioning storage! All in all it comes down to setting you expectations and your budget. Probably adjusting your expectations according to your budget :). Processors As a rule of thumb you want VT-D (virtualization) technology built in to the processor allowing you to have 64 bit machines running on your host. Memory The more the better! If you are building a home lab don’t bother with ECC unless you are going to run machines that absolutely should be on all the time and your comfort depends on it! Motherboard Depends on what you are going to do with storage: If you are going the NAS way then the number of SATA port/RAID capabilities do not really matter. If you decide to have a single server with lots of dedicated storage it obviously matters how much SATA ports you will have, alternatively you could use a RAID controller (but these set you back a pretty penny if you want one. DELL 6i’s are usually available for a good bargain if you can find one!). Easiest is to get one with a built-in graphics card (on-board) as you are just adding more heat, power usage and possible points of failure. Networking Just like your choice of motherboard the networking side tends to depend on how you want to go. A single virtualization  host with local storage can usually get away with having a single network card, a cluster or server which uses iSCSI storage tends to have more than one teamed up :). Storage The dreaded beast from the dark! The horror which lives in the forest! The most difficult decision you are going to make in the building of your lab. Why you might ask? Simple my friend, having the right choice of storage can make or break your virtualization solution. The performance of you storage choice will have an important impact on the responsiveness of your virtual machines and the deployment of new machines. It also makes a run with your budget! If you decide to go the NAS route you will be dropping a lot more money than if you would be having just a bunch of disks sitting in a server and manually distributing the virtual machines over the disks. Platform I’m a Microsoftee so Hyper-V is a dead giveaway for me. If you are interested in using VMware I won’t stop you but the rest of my posts will be oriented on Server 2012 Hyper-V (aka 3.0)! What did I use? Before someone asks me this in the comments I’ll give you a quick run down of what I am using. - Intel 2.4 quad core processors (i something something) - 24 GB DDR3 Memory - Single disk in each server (might look at this as I move the servers to 2012) - Synology DS1812+ NAS - 3 network interfaces where possible - HP1800 procurve managed switch I decided to spring for the NAS as I will also be using it for backups and media storage (which is working out quite nicely with my Xbox 360 I must say). At the time of building my 2 boxes (over a year and a half ago) these set me back about 900 euros each so I can image you can build the same or better for a lower price. Next article will be diagramming what I want to achieve and starting a build on the Hyper V 3.0 cluster!

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• Cloud – the forecast is improving

  - by Rob Farley

  There is a lot of discussion about “the cloud”, and how that affects people’s data stories. Today the discussion enters the realm of T-SQL Tuesday, hosted this month by Jorge Segarra. Over the years, companies have invested a lot in making sure that their data is good, and I mean every aspect of it – the quality of it, the security of it, the performance of it, and more. Experts such as those of us at LobsterPot Solutions have helped these companies with this, and continue to work with clients to make sure that data is a strong part of their business, not an oversight. Whether business intelligence systems are being utilised or not, every business needs to be able to rely on its data, and have the confidence in it. Data should be a foundation upon which a business is built. In the past, data had been stored in paper-based systems. Filing cabinets stored vital information. Today, people have server rooms with storage of various kinds, recognising that filing cabinets don’t necessarily scale particularly well. It’s easy to ‘lose’ data in a filing cabinet, when you have people who need to make sure that the sheets of paper are in the right spot, and that you know how things are stored. Databases help solve that problem, but still the idea of a large filing cabinet continues, it just doesn’t involve paper. If something happens to the physical ‘filing cabinet’, then the problems are larger still. Then the data itself is under threat. Many clients have generators in case the power goes out, redundant cables in case the connectivity dies, and spare servers in other buildings just in case they’re required. But still they’re maintaining filing cabinets. You see, people like filing cabinets. There’s something to be said for having your data ‘close’. Even if the data is not in readable form, living as bits on a disk somewhere, the idea that its home is ‘in the building’ is comforting to many people. They simply don’t want to move their data anywhere else. The cloud offers an alternative to this, and the human element is an obstacle. By leveraging the cloud, companies can have someone else look after their filing cabinet. A lot of people really don’t like the idea of this, partly because the administrators of the data, those people who could potentially log in with escalated rights and see more than they should be allowed to, who need to be trusted to respond if there’s a problem, are now a faceless entity in the cloud. But this doesn’t mean that the cloud is bad – this is simply a concern that some people may have. In new functionality that’s on its way, we see other hybrid mechanisms that mean that people can leverage parts of the cloud with less fear. Companies can use cloud storage to hold their backup data, for example, backups that have been encrypted and are therefore not able to be read by anyone (including administrators) who don’t have the right password. Companies can have a database instance that runs locally, but which has its data files in the cloud, complete with Transparent Data Encryption if needed. There can be a higher level of control, making the change easier to accept. Hybrid options allow people who have had fears (potentially very justifiable) to take a new look at the cloud, and to start embracing some of the benefits of the cloud (such as letting someone else take care of storage, high availability, and more) without losing the feeling of the data being close. @rob_farley

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• MySQL Server 5.6 default my.cnf and my.ini

  - by user12626240

  We've introduced a default my.cnf / my.ini file for MySQL Server that you can now see in the 5.6.8 release candidate: # For advice on how to change settings please see # http://dev.mysql.com/doc/refman/5.6/en/server-configuration-defaults.html [mysqld] # Remove leading # and set to the amount of RAM for the most important data # cache in MySQL. Start at 70% of total RAM for dedicated server, else 10%. # innodb_buffer_pool_size = 128M   # Remove leading # to turn on a very important data integrity option: logging # changes to the binary log between backups. # log_bin   # These are commonly set, remove the # and set as required. # basedir = ..... # datadir = ..... # port = ..... # socket = ..... # server_id = .....   # Remove leading # to set options mainly useful for reporting servers. # The server defaults are faster for transactions and fast SELECTs. # Adjust sizes as needed, experiment to find the optimal values. # join_buffer_size = 128M # sort_buffer_size = 2M # read_rnd_buffer_size = 2M   sql_mode=NO_ENGINE_SUBSTITUTION,STRICT_TRANS_TABLES    There is also a template file called my-default.cnf or my-default.ini that has these lines near the start: # *** DO NOT EDIT THIS FILE. It's a template which will be copied to the # *** default location during install, and will be replaced if you # *** upgrade to a newer version of MySQL.   On Linux systems, the mysql_install_db command will copy the template file to the final location, where the server will read and use the file, removing the extra three lines. On Windows, the installer will create extra settings based on the answers you gave during installation. Neither will overwrite an existing my.cnf or my.ini file. The only initially active setting here is to change the value of  sql_mode from the server default of NO_ENGINE_SUBSTITUTION to NO_ENGINE_SUBSTITUTION,STRICT_TRANS_TABLES. This strict mode changes warnings for some non-standard behaviour into errors. This can cause applications which rely on the non-standard things, like dates that aren't valid, to lose data. If we had just changed the server default, the new setting would affect all servers that lack an explicit sql_mode setting, including those where strict mode is harmful. So we did it in the default file instead because that will only affect new server installations. You should expect that in our next version after 5.6, the server default will include STRICT_TRANS_TABLES. Our Windows installer and some of our connectors already use STRICT_TRANS_TABLES by default. Strict has been our preferred setting for many years and it is good to see some development platforms are using it. If you need the old behaviour, just remove the STRICT_TRANS_TABLES setting. If you do this, please also ask your application provider to make it unnecessary. They can do that by setting the session sql_mode setting in their own connections, so the rest of the applications using the server don't have to have an undesirable default. We've kept this file as small as possible because we found that our old files were too big and confused people. We've also now removed the old my-huge and related example files. One key part of this is the link to the documentation, where we will provide an introduction to some key settings. We'd like to hear your feedback on settings that will benefit most users or are most important to call out for existing users. Please do that by commenting here or if you prefer by adding comments to this bug report.

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• SQLite vs Firebird

  - by rwallace

  The scenario I'm looking at is "This program uses Postgres. Oh, you want to just use it single-user for the moment, and put off having to deal with installing a database server? Okay, in the meantime you can use it with the embedded single-user database." The question is then which embedded database is best. As I understand it, the two main contenders are SQLite and Firebird; so which is better? Criteria: Full SQL support, or as close as reasonably possible. Full text search. Easy to call from C# Locks, or allows you to lock, the database file to make sure nobody tries to run it multiuser and ends up six months down the road with intermittent data corruption in all their backups. Last but far from least, reliability. As I understand it, the disadvantages of SQLite are, No right outer join. Workaround: use left outer join instead. Not much integrity checking. Workaround: be really careful in the application code. No decimal numbers. Workaround: lots of aspirin. None of the above are showstoppers. Are there any others I'm missing? (I know it doesn't support some administrative and code-within-database SQL features, that aren't relevant for this kind of use case.) I don't know anything much about Firebird. What are its disadvantages?

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• People not respecting good practices at workplace

  - by VexXtreme

  Hi There are some major issues in my company regarding practices, procedures and methodologies. First of all, we're a small firm and there are only 3-4 developers, one of which is our boss who isn't really a programmer, he just chimes in now and then and tries to do code some simple things. The biggest problems are: Major cowboy coding and lack of methodologies. I've tried explaining to everyone the benefits of TDD and unit testing, but I only got weird looks as if I'm talking nonsense. Even the boss gave me the reaction along the lines of "why do we need that? it's just unnecessary overhead and a waste of time". Nobody uses design patterns. I have to tell people not to write business logic in code behind, I have to remind them not to hardcode concrete implementations and dependencies into classes and cetera. I often feel like a nazi because of this and people think I'm enforcing unnecessary policies and use of design patterns. The biggest problem of all is that people don't even respect common sense security policies. I've noticed that college students who work on tech support use our continuous integration and source control server as a dump to store their music, videos, series they download from torrents and so on. You can imagine the horror when I realized that most of the partition reserved for source control backups was used by entire seasons of TV series and movies. Our development server isn't even connected to an UPS and surge protection. It's just plugged straight into the wall outlet. I asked the boss to buy surge protection, but he said it's unnecessary. All in all, I like working here because the atmosphere is very relaxed, money is good and we're all like a family (so don't advise me to quit), but I simply don't know how to explain to people that they need to stick to some standards and good practices in IT industry and that they can't behave so irresponsibly. Thanks for the advice

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• Java OutOfMemoryError due to Linux RAM disk cache not freed

  - by Markus Jevring

  The process will run fine all day, then, bam, without warning, it will throw this error. Sometimes seemingly in the middle of doing nothing. It will happen at seemingly random times during the day. I checked to see if anything else was running on the machine, like scheduled backups or something, but found nothing. The machine has enough physical memory (2GB, with about 1GB free for a 3-500MB load), and has sufficient -Xmx specified. According to our sysadmin, the problem is that the RAM that the kernel uses as a disk cache (apparently all but 8MB) is not freed when the JVM needs to allocate memory, so the JVM process throws an OutOfMemoryError. This could be because Java asks the kernel if enough memory is available before allocating and finds that it is insufficient, resulting in a crash. I would like to think, however, that Java simply tries to allocate the memory via the kernel, and when the kernel gets such a request, it makes room for the application by throwing our some of the disk cache. Has anyone else run in to the issue, and if so, what was the error, and how did you solve it? We are currently using jdk1.6.0_20 on SLES 10 SP2 Linux 2.6.16.60-0.42.9-smp in VMWare ESX.

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• java distributed cache for low latency, high availability

  - by Shahbaz

  I've never used distributed caches/DHTs like memcached, jboss cache, ehcache, etc. I'm wondering which, if any, is appropriate for my use. First, I'm not doing web applications (as most of these project seem to be geared towards web apps). I write servers (Order Management Systems actually) for financial trading firms. The servers themselves are not too complicated. They need to receive information (market data, orders, executions, etc.) rout them to their destination while possibly transforming some of these messages. I am looking at these products to solve the following problems: * Safe repository of the state of the server. I'd rather build the logic of my application as a bunch of transformers (similar to Apache Camel) and store the state in a 'safe' place * This repository should be distributed: in case one of these data stores crashes, one or two more should be up and I should be able to switch to them seamlessly * This repository should be fast. Single digits milliseconds count here, in other words, systems which consume/process this data are automated systems, not humans clicking on links. This system needs to have high-throughput and low latency. By sending my data outside the process, I am necessarily slowing performance, but I am trying to balance absolute raw speed and absolute protection of data. * This repository should be safe. Similar to the point about several on-line backups, this system needs to write data to disk (potentially more than one disk). I'd really like to stop writing my own 'transaction servers.' Am I correct to be looking into projects such as jboss cache, ehcache, etc.? Thanks

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• How can I store HTML in a Doctrine YML fixture

  - by argibson

  I am working with a CMS-type site in Symfony 1.4 (Doctrine 1.2) and one of the things that is frustrating me is not being able to store HTML pages in YML fixtures. Instead I have to create SQL backups of the data if I want to drop and rebuild which is a bit of a pest when Symfony/Doctrine has a fantastic mechanism for doing exactly this. I could write a mechanism that reads in a set of HTML files for each page and fills the data in that way (or even write it as a task). But before I go down that road I am wondering if there is any way for HTML to be stored in a YML fixture so that Doctrine can simply import it into the database. Update: I have tried using symfony doctrine:data-dump and symfony doctrine:data-load however despite the dump correctly creating the fixture with the HTML, the load task appears to 'skip' the value of the column with the HTML and enters everything else into the row. In the database the field doesn't show up as 'NULL' but rather empty so I believe Doctrine is adding the value of the column as ''. Below is a sample of the YML fixture that symfony doctrine:data-dump created. I have tried running symfony doctrine:data-load against various forms of this including removing all the escaped characters (new lines and quotes leaving only angle brackets) but it still doesn't work. Product_69: name: 'My Product' Developer: Developer_30 tagline: 'Text that briefly describes the product' version: '2008' first_published: '' price_code: A79 summary: '' box_image: '' description: "<div id=\"featureSlider\">\n <ul class=\"slider\">\n <li class=\"sliderItem\" title=\"Summary\">\n <div class=\"feature\">\n Some text goes in here</div>\n </li>\n </ul>\n </div>\n" is_visible: true

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• SQL Server: Is it possible to prevent SQL Agent from failing a step on error?

  - by Kenneth

  I have a stored procedure that runs custom backups for around 60 SQL servers (mixes 2000 through 2008R2). Occasionally, due to issues outside of my control (backup device inaccessible, network error, etc.) an individual backup on one or two databases will fail. This causes this entire step to fail, which means any subsequent backup commands are not executed and half of the databases on a given server may not be backed up. On the 2005+ boxes I am using TRY/CATCH blocks to manage these problems and continue backing up the remaining databases. On a 2000 server however, for example, I have no way to prevent this error from failing the entire step: Msg 3201, Level 16, State 1, Line 1 Cannot open backup device 'db-diff(\PATH\DB-DIFF-03-16-2010.DIF)'. Operating system error 5(Access is denied.). Msg 3013, Level 16, State 1, Line 1 BACKUP DATABASE is terminating abnormally. I am simply asking if anything like TRY/CATCH is possible in SQL 2000? I realize there are no built in methods for this, so I guess I am looking for some creativity. Even when wrapping each backup (or any failing statement) via sp_executesql the job fails instantly. Example: DECLARE @x INT, @iReturn INT PRINT 'Executing statement that will fail with 208.' EXEC @iReturn = Sp_executesql N'SELECT * from TABLETHATDOESNTEXIST;' PRINT Cast(@iReturn AS NVARCHAR) --In SSMS this return code prints. Executed as a job it fails and aborts before this statement.

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• Where are the real risks in network security?

  - by Barry Brown

  Anytime a username/password authentication is used, the common wisdom is to protect the transport of that data using encryption (SSL, HTTPS, etc). But that leaves the end points potentially vulnerable. Realistically, which is at greater risk of intrusion? Transport layer: Compromised via wireless packet sniffing, malicious wiretapping, etc. Transport devices: Risks include ISPs and Internet backbone operators sniffing data. End-user device: Vulnerable to spyware, key loggers, shoulder surfing, and so forth. Remote server: Many uncontrollable vulnerabilities including malicious operators, break-ins resulting in stolen data, physically heisting servers, backups kept in insecure places, and much more. My gut reaction is that although the transport layer is relatively easy to protect via SSL, the risks in the other areas are much, much greater, especially at the end points. For example, at home my computer connects directly to my router; from there it goes straight to my ISPs routers and onto the Internet. I would estimate the risks at the transport level (both software and hardware) at low to non-existant. But what security does the server I'm connected to have? Have they been hacked into? Is the operator collecting usernames and passwords, knowing that most people use the same information at other websites? Likewise, has my computer been compromised by malware? Those seem like much greater risks. What do you think?

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• How to I display results of phpcs in VIM?

  - by Matt

  I am presently trying to use PHP Codesniffer (PEAR) in vim for PHP Files. I have found 2 sites that give code to add into the $HOME/.vim/plugin/phpcs.vim file. I have added the code and I "think" it is working, but I cannot see the results, I only see one line at the very bottom of vim that says (1 of 32) but I cannot see any of the 32 errors. Here is my .vimrc file " Backup Options -> Some People may not want this... it generates extra files set backup " Enable Backups set backupext=.bak " Add .bak extention to modified files set patchmode=.orig " Copy original file to with .orig extention Before saving. " Set Tabs and spacing for PHP as recomended by PEAR and Zend set expandtab set shiftwidth=4 set softtabstop=4 set tabstop=4 " Set Auto-indent options set cindent set smartindent set autoindent " Show lines that exceed 80 characters match ErrorMsg '\%80v.\+' " Set Colors set background=dark " Show a status bar set ruler set laststatus=2 " Set Search options highlight, and wrap search set hls is set wrapscan " File Type detection filetype on filetype plugin on " Enable Spell Checking set spell " Enable Code Folding set foldenable set foldmethod=syntax " PHP Specific options let php_sql_query=1 " Highlight sql in php strings let php_htmlInStrings=1 " Highlight HTML in php strings let php_noShortTags=1 " Disable PHP Short Tags let php_folding=1 " Enable Ability to FOLD html Code I have tried 2 different versions of phpcs.vim, and I get the same results for both: Version 1 (found at: VIM an a PHP IDE) function! RunPhpcs() let l:filename=@% let l:phpcs_output=system('phpcs --report=csv --standard=YMC '.l:filename) " echo l:phpcs_output let l:phpcs_list=split(l:phpcs_output, "\n") unlet l:phpcs_list[0] cexpr l:phpcs_list cwindow endfunction set errorformat+=\"%f\"\\,%l\\,%c\\,%t%*[a-zA-Z]\\,\"%m\" command! Phpcs execute RunPhpcs() Version 2: (found at Integrated PHP Codesniffer in VIM ) function! RunPhpcs() let l:filename=@% let l:phpcs_output=system('phpcs --report=csv --standard=YMC '.l:filename) let l:phpcs_list=split(l:phpcs_output, "\n") unlet l:phpcs_list[0] cexpr l:phpcs_list cwindow endfunction set errorformat+="%f"\\,%l\\,%c\\,%t%*[a-zA-Z]\\,"%m" command! Phpcs execute RunPhpcs() Both of these produce identical results. phpcs is installed on my system, and I am able to generate results outside of vim. Any help would be appreciated I am just learning more about vim...

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• How to properly develop and deploy features for existing asp.net applications on IIS

  - by Tomh

  My question actually consists of multiple questions. I'm frequently reading about companies who deploy a small subset of features for a select amount of customers using the live "database". Ruby on Rails and its ecosystem have deployment tools and database migrations to deploy or rollback such features in a live production or staging environment. My question, how is this done for an asp.net (mvc in particular) application? How do you test your newly released features against live data? Do you have any tools to modify the existing database and roll back changes if necessary? Do you make backups before deployment? Update Maybe I should point out that my question is not really clear, getting more answers here will help me phrase the question better. To make it easier I will describe a situation I'm commonly seeing with some of my clients. My clients have large deployments of popular web applications. They do not have staging/QA/testing servers. (yes this is not optimal). The data their apps consist of are images, xml files, user uploads and data in Sql Server. Having a few records, of their production database and a couple of dummy files is not a substitute of testing against real data in my opinion. How would you design a workflow that can create a acceptable environment to mimic a production environment before going live?

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• Payment Processors - What do I need to know if I want to accept credit cards on my website?

  - by Michael Pryor

  This question talks about different payment processors and what they cost, but I'm looking for the answer to what do I need to do if I want to accept credit card payments? Assume I need to store credit card numbers for customers, so that the obvious solution of relying on the credit card processor to do the heavy lifting is not available. PCI Data Security, which is apparently the standard for storing credit card info, has a bunch of general requirements, but how does one implement them? And what about the vendors, like Visa, who have their own best practices? Do I need to have keyfob access to the machine? What about physically protecting it from hackers in the building? Or even what if someone got their hands on the backup files with the sql server data files on it? What about backups? Are there other physical copies of that data around? Tip: If you get a merchant account, you should negotiate that they charge you "interchange-plus" instead of tiered pricing. With tiered pricing, they will charge you different rates based on what type of Visa/MC is used -- ie. they charge you more for cards with big rewards attached to them. Interchange plus billing means you only pay the processor what Visa/MC charges them, plus a flat fee. (Amex and Discover charge their own rates directly to merchants, so this doesn't apply to those cards. You'll find Amex rates to be in the 3% range and Discover could be as low as 1%. Visa/MC is in the 2% range). This service is supposed to do the negotiation for you (I haven't used it, this is not an ad, and I'm not affiliated with the website, but this service is greatly needed.) This blog post gives a complete rundown of handling credit cards (specifically for the UK).

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• Is the RESTORE process dependent on schema?

  - by Martin Aatmaa

  Let's say I have two database instances: InstanceA - Production server InstanceB - Test server My workflow is to deploy new schema changes to InstanceB first, test them, and then deploy them to InstanceA. So, at any one time, the instance schema relationship looks like this: InstanceA - Schema Version 1.5 InstanceB - Schema Version 1.6 (new version being tested) An additional part of my workflow is to keep the data in InstanceB as fresh as possible. To fulfill this, I am taking the database backups of InstanceA and applying them (restoring them) to InstanceB. My question is, how does schema version affect the restoral process? I know I can do this: Backup InstanceA - Schema Version 1.5 Restore to InstanceB - Schema Version 1.5 But can I do this? Backup InstanceA - Schema Version 1.5 Restore to InstanceB - Schema Version 1.6 (new version being tested) If no, what would the failure look like? If yes, would the type of schema change matter? For example, if Schema Version 1.6 differed from Schema Version 1.5 by just having an altered storec proc, I imagine that this type of schema change should't affect the restoral process. On the other hand, if Schema Version 1.6 differed from Schema Version 1.5 by having a different table definition (say, an additional column), I image this would affect the restoral process. I hope I've made this clear enough. Thanks in advance for any input!

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• Powershell - Splitting string into seperate components

  - by TheD

  I am writing a script which will basically do the following: Read from a text file some arguements: DriveLetter ThreeLetterCode ServerName VolumeLetter Integer Eg. W MSS SERVER01 C 1 These values happen to form a folder destination W:\MSS\, and a filename which works in the following naming convention: SERVERNAME_VOLUMELETTER_VOL-b00X-iYYY.spi - Where The X is the Integer above The value Y I need to work out later, as this happens to be the value of the incremental image (backups) and I need to work out the latest incremental. So at the moment -- Count lines in file, and loop for this many lines. $lines = Get-Content -Path PostBackupCheck-Textfile.txt | Measure-Object -Line for ($i=0; $i -le $lines.Lines; $i++) Within this loop I need to do a Get-Content to read off the line I am currently looking at i.e. line 0, line 1, line 2, as there will be multiple lines in the format I wrote at the beginning and split the line into an array, whereby each part of the file, as seen above naming convention, is in a[0], a[1], a[2]. etc The reason for this is because, I need to then sort the folder that contains these, find the latest file, by date, and take the _iXXX.spi part and place this into the array value a[X] so I then have a complete filename to mount. This value will replace iYYY.spi It's a little complex because I also have to make sure when I do a Get-ChildItem with -Include before I sort it all by date, I am only including the filename that matches the arguements fed to it from the text file : So, SERVER01_C_VOL-b001-iYYY.spi and not anything else. i.e. not SERVER01_D_VOL-b001-iYYY.spi Then take the iYYY value from the sort on the Get-ChildItem -Include and place that into the appropriate array item. I've literally no idea where to start, so any ideas are appreciated! Hopefully I've explained in enough detail. I have also placed the code on Pastebin: http://pastebin.com/vtFifTW6 Thanks!

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• How to migrate primary key generation from "increment" to "hi-lo"?

  - by Bevan

  I'm working with a moderate sized SQL Server 2008 database (around 120 tables, backups are around 4GB compressed) where all the table primary keys are declared as simple int columns. At present, primary key values are generated by NHibernate with the increment identity generator, which has worked well thus far, but precludes moving to a multiprocessing environment. Load on the system is growing, so I'm evaluating the work required to allow the use of multiple servers accessing a common database backend. Transitioning to the hi-lo generator seems to be the best way forward, but I can't find a lot of detail about how such a migration would work. Will NHibernate automatically create rows in the hi-lo table for me, or do I need to script these manually? If NHibernate does insert rows automatically, does it properly take account of existing key values? If NHibernate does take care of thing automatically, that's great. If not, are there any tools to help? Update NHibernate's increment identifier generator works entirely in-memory. It's seeded by selecting the maximum value of used identifiers from the table, but from that point on allocates new values by a simple increment, without reference back to the underlying database table. If any other process adds rows to the table, you end up with primary key collisions. You can run multiple threads within the one process just fine, but you can't run multiple processes. For comparison, the NHibernate identity generator works by configuring the database tables with identity columns, putting control over primary key generation in the hands of the database. This works well, but compromises the unit of work pattern. The hi-lo algorithm sits inbetween these - generation of primary keys is coordinated through the database, allowing for multiprocessing, but actual allocation can occur entirely in memory, avoiding problems with the unit of work pattern.

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• Suggestions for a Cron like scheduler in Python?

  - by jamesh

  I'm looking for a library in Python which will provide at and cron like functionality. I'd quite like have a pure Python solution, rather than relying on tools installed on the box; this way I run on machines with no cron. For those unfamiliar with cron: you can schedule tasks based upon an expression like: 0 2 * * 7 /usr/bin/run-backup # run the backups at 0200 on Every Sunday 0 9-17/2 * * 1-5 /usr/bin/purge-temps # run the purge temps command, every 2 hours between 9am and 5pm on Mondays to Fridays. The cron time expression syntax is less important, but I would like to have something with this sort of flexibility. If there isn't something that does this for me out-the-box, any suggestions for the building blocks to make something like this would be gratefully received. Edit I'm not interested in launching processes, just "jobs" also written in Python - python functions. By necessity I think this would be a different thread, but not in a different process. To this end, I'm looking for the expressivity of the cron time expression, but in Python. Cron has been around for years, but I'm trying to be as portable as possible. I cannot rely on its presence.

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