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• ZFS + FreeBSD + virtualbox

  - by John

  Hi, I'm configuring a FreeBSD server hosting virtualbox serving half dozen mission critical busy mail servers. I just learned ZFS, I'm quite attracted, but have a few questions: what is the CPU overhead of ZFS? I googled and found little (or no) benchmark for that. from what I learned, when ZFS updates files, it keeps the old file as snapshot, and write the updated part for the new version. However that would mean for each snapshot it keeps that require significant storage overhead. How much is this storage overhead? For example, suppose I have 2TB usable space, how much space can actually be used for the latest version of files one year later? is FreeBSD with ZFS hosting virtualbox serving half dozen busy guest mission critical mail servers a reasonable combination? Anything particular to be careful with? And can I still choose ZFS for the guest OSs? This is because I may build another identical such box for redundancy, and will need to do some mirroring between each pair of the guest systems across the boxes. I'm trying to configure a Dell R710 for this. From what I learned, I shouldn't choose any RAID at all, is that true? In that case, are the drives still arrive hot swappable? this may sounds a bit pathetic, but since I have no experience with ZFS at all, and this is a mission critical server, so just ask just in case: I'm choosing twin Intel L5630 processors, and 6 x 600GB 15K RPM Serial-Attach SCSI drives. If I need more space in the future, I would just hot swap some drivers with larger capacity to expand the storage. There is no problem with these, right?

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• How to get the permissions right for /dev/raw1394

  - by Mark0978

  I recently upgraded one of my ubuntu machines to Karmic and I'm having trouble getting the permissions of /dev/raw1394 set to 0666. They only thing this machine is used for is recording audio from a firepod which uses /dev/raw1394 via jackd and there are no other FireWire devices connected, so security around this device is not really an issue. If I run as root, everything works as expected, but I have some folks that run the recorder that I don't want to have root access. However, I can't figure out which lines setup the perms I've tied this: /etc/udev/permissions.d/raw1394.rules:raw1394:root:root:0666 And I have this setup (default install) /lib/udev/rules.d/75-persistent-net-generator.rules:SUBSYSTEMS=="ieee1394", ENV{COMMENT}="Firewire device $attr{host_id})" /lib/udev/rules.d/75-cd-aliases-generator.rules:# the "path" of usb/ieee1394 devices changes frequently, use "id" /lib/udev/rules.d/75-cd-aliases-generator.rules:ACTION=="add", SUBSYSTEM=="block", SUBSYSTEMS=="usb|ieee1394", ENV{ID_CDROM}=="?*", ENV{GENERATED}!="?*", \ /lib/udev/rules.d/60-persistent-storage-tape.rules:KERNEL=="st*[0-9]|nst*[0-9]", ATTRS{ieee1394_id}=="?*", ENV{ID_SERIAL}="$attr{ieee1394_id}", ENV{ID_BUS}="ieee1394" /lib/udev/rules.d/50-udev-default.rules:# FireWire (deprecated dv1394 and video1394 drivers) /lib/udev/rules.d/50-udev-default.rules:KERNEL=="dv1394-[0-9]*", NAME="dv1394/%n", GROUP="video" /lib/udev/rules.d/50-udev-default.rules:KERNEL=="video1394-[0-9]*", NAME="video1394/%n", GROUP="video" /lib/udev/rules.d/60-persistent-storage.rules:KERNEL=="sd*[!0-9]|sr*", ATTRS{ieee1394_id}=="?*", SYMLINK+="disk/by-id/ieee1394-$attr{ieee1394_id}" /lib/udev/rules.d/60-persistent-storage.rules:KERNEL=="sd*[0-9]", ATTRS{ieee1394_id}=="?*", SYMLINK+="disk/by-id/ieee1394-$attr{ieee1394_id}-part%n" And I find these lines in /var/log/syslog Apr 30 09:11:30 record kernel: [ 3.284010] ieee1394: Node added: ID:BUS[0-00:1023] GUID[000a9200c7062266] Apr 30 09:11:30 record kernel: [ 3.284195] ieee1394: Host added: ID:BUS[0-01:1023] GUID[00d0035600a97b9f] Apr 30 09:11:30 record kernel: [ 18.372791] ieee1394: raw1394: /dev/raw1394 device initialized What I can't figure out, is which line actually creates that raw1394 device in the first place. How do you get /dev/raw1394 to have permissions 0666?

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• ZFS: Mirror vs. RAID-Z

  - by John Clayton

  I'm planning on building a file server using OpenSolaris and ZFS that will provide two primary services - be an iSCSI target for XenServer virtual machines & be a general home file server. The hardware I'm looking at includes 2x 4-port SATA controllers, 2x small boot drives (one on each controller), and 4x big drives for storage. This allows one free port per controller for upgrading the array down the road. Where I'm a little confused is how to setup the storage drives. For performance, mirroring appears to be king. I'm having a hard time seeing what the benefit would be of using RAIDZ over mirroring would be. With this setup I can see two options - two mirrored pools in one stripe, or RAIDZ2. Both should protect against 2 drive failures, and/or one controller failure...the only benefit of RAIDZ2 would be that any 2 drives could fail. The storage should be 50% of capacity in both cases, but the first should have much better performance, right? The other thing I'm trying to wrap my mind around is the benefit of mirrored arrays with more than two devices. For data integrity what, if any, would be the benefit of a RAIDZ over a three-way mirror? Since ZFS maintains file integrity what does RAIDZ bring to the table...doesn't ZFS's integrity checks negate the value of RAIDZ's parity?

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• 0 connected nodes in datastax opscenter

  - by gansbrest

  Installed opscenterd on the separate node outside of the cluster, but within firewall ( aws security group ). Tested all possible ports between agents and opcenter server. No errors in the log.. 2013-10-30 01:07:23+0000 [FC_Cluster] INFO: Initializing event storage. 2013-10-30 01:07:23+0000 [FC_Cluster] INFO: Attempting to load all persisted alert rules 2013-10-30 01:07:23+0000 [FC_Cluster] INFO: Done loading persisted alert rules 2013-10-30 01:07:23+0000 [FC_Cluster] INFO: Done initializing event storage. 2013-10-30 01:07:23+0000 [FC_Cluster] INFO: Done loading persisted scheduled job descriptions 2013-10-30 01:07:23+0000 [FC_Cluster] INFO: OpsCenter starting up. 2013-10-30 01:07:23+0000 [] INFO: Finished starting new cluster services for FC_Cluster 2013-10-30 01:08:04+0000 [FC_Cluster] INFO: Agent for ip 10.34.10.185 is version u'3.2.2' 2013-10-30 01:08:04+0000 [FC_Cluster] INFO: Agent for ip 10.32.37.251 is version u'3.2.2' 2013-10-30 01:08:04+0000 [FC_Cluster] INFO: Agent for ip 10.82.226.252 is version u'3.2.2' The most interesting part that I can see some data in the opscenter UI, when I stop agents, there is no data displayed, when I start - it show up again, but at the same time it shows 0 connected nodes. Storage capacity is even funnier - 3 of 0 nodes.. Any ideas why that could be happening?

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• VMware vSphere 4.1 and BackupExec 2010

  - by Josh

  I'm sure a common problem with most shops is backups, their size, and the window in which you have to back up the data. What we are working with: VMware vSphere 4.1 Cluster PS4000XV Equallogic Storage Array (1.6TB Volume dedicated for Backup to Disk) Physical Backup Server with a single LTO4 drive. BackupExec 2010 R3 with the following agents, Exchange, SQL, Active Directory, VMware. Dual Gigabit MPIO Connections between all devices (Storage Array, Backup Server, VM Hosts) What we would like to accomplish: I would like to implement an efficient Backup to Disk to Tape solution where all of our VMs are backed up to the Storage Array first, and then once completely backed up to the array are replicated to tape. In the event we needed to recover, we would be able to do so directly from tape. Where we are at currently. Of the several ways I have setup the jobs in Backup Exec 2010 R3 the backup jobs all queue up at the same time, as soon as a job is finished backing up to disk it then starts that same job to tape, but pulling from the original source instead of the designated B2D location. I understand that I could create a job that backs up the "Backup to Disk" folder to tape, but in the event of restoration, I would first need to stage the data in the B2D folder before I could restore the VM. I would really like to hear from individuals in similar situations. Any and all comments and critiques are appreciated.

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• cPanel web servers mounting home partition to a NAS or SAN

  - by Scott

  I currently have 2 cPanel web servers that are little 1RU dual cpu quad core xeons. They have a lot of resources for processing and handling web requests, and never exceed more than 10% cpu usage. They also have plenty of RAM. The problem is though that they both have RAID 1 160Gb SAS hard disk drives in them that are 75% full, and growing by the day. I didnt think that the amount of disk usage would be so high, but due to the nature of the sites hosted, this has become an issue. The easy fix would be just to upgrade the hard drives to something bigger (probably not of the SAS variety), but I am thinking of keeping the current machines as "processing servers" and buying a central "storage server" with about 12TB of storage. The /home/ partition on each of the 1RU servers would be mounted to a NAS or SAN point on this central storage server. My questions are: - Has anyone got a cPanel setup where they mount /home/ to a NAS or SAN elsewhere? If so, can you provide details as to what you did and how it went :) - Any recommendations on networking? Is gigabit ethernet enough? Is TCP/IP going to be a noticable performance problem? Anyone used a TOE key? - Anyone benchmarked or had any performance issues with SAN over NAS? Any help greatly appreciated. Scott

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• ESX 4.0 space: DASD, NAS, or ?

  - by thormj

  I put together an ESX box for better management, but its performance is a WTF item; I'm a noob at dealing with ESX, so I'm looking for a laundry-list of reading material to help me straighten this out so I can go back to .NET programming. Current storage system: We're running Raid5+Hotspare (8x500 GB spindles) on a PERC6i on a Dell 2910. Due to ESX limitatios, the PERC is showing the storage as 1x2TB + 1x800GB "partitions." I'm not sure of the setup's configuration (stride / stripe / ???) at all. Our Applications We have a SBS server as well as a minor (2x50 GB, but growing at 10GB/month) database server... Our application that lives on the database VM is CPU and I/O insense; it's a database churning excercise mixed in with a lot of computation on the data (fixing that performance is what I'm supposed to be working on)... Perfomance Issue When I do a backup, restore, or worse (copy a backup from 1 vm to another to move it to the QA VM), the entire system slows to a crawl (even "unrelated" VMs). I originally thought a DASD situation would be quite good since you had PCI-x bandwidth, but the systemwide slowdown is killing productivity. Questions What should I do to make an intelligent decision about NAS vs RAID vs SAN vs DASD? Are there sweet spots/ugly spots in the storage setup? Can you use a SSD PCI-X card in ESX for the tempdb? Good/Bad idea? Is there any way to "share" some image in a copy-on-write fashion? Most of the "Backup-Copy-Restore" is to "put a clean image on the dev boxes"; if I could have them "share" the master image, the "big copy" (2x50 GB) would only need to be done once per week instead of once per dev per week...[runtime performance isn't a concern with the dev boxes, but the backup/copy/restore kills production, SBS, and everything else on the box]

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• Is it possible/practical to install and run Linux on a USB flash drive?

  - by Graeme Donaldson

  I'm going to replace my old 2004 vintage desktop PC soon and I have an idea of what I want to do, I'm just not sure if it's possible or realistic. In the time since I built the old PC it has slowly become less used as a PC and more as a file server, so I figured I'd build a small file server which could also function as a router/DHCP/DNS/whatever box. The idea is to base it on an Atom system. I have my eye on the Intel D510MO for the moment. This supports 2 SATA disks, and I'd prefer to dedicate those to data storage. I'd like to install Ubuntu Server or maybe Debian on a 8/16GB USB flash drive. I have seen plenty of tutorials on how to perform an installation from a USB drive, but I can't seem to find any info on actually booting and running the OS from USB flash. Is this even possible? Is it practical? This box will mostly be used for: Making backups of mine and my wife's notebooks via LAN. Will use SMB or NFS for this. Digital media storage, which will be accessed by a Mede8er box with no storage of its own. I will most likely use NFS for this.

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• Windows XP Setup Fails to Recognize USB Floppy after formatting AHCI disk

  - by Strahn

  I am attempting to install Windows XP Professional x64 onto a HP EliteBook 8540w. I have downloaded both the latest Intel Rapid Storage Technology drivers and the Intel Storage Matrix drivers that are listed on HPs website and copied the drivers over to a floppy disk (two separate floppies, one for each version of the drivers.) Booting to my WinXP Pro x64 install CD, I go through the F6 process, load the driver and am able to see my HDD, delete, create and format partitions on it. When I go to continue the install, after checking the disk, the system asks me to enter the disk labeled "Intel Rapid Storage Technology" and press enter to continue. Nothing happens at this point when I press enter. This happens if I use the latest drivers or the older drivers. We have created a slipstreamed install CD using nLite that has the AHCI drivers integrated, which installs fine. However, we have identified a number of issues with the system that I believe are side-effects of using nLite for the slipstreaming and I am attempting to verify that. I have researched this issue and found a few examples of others having the same problem, but no solution. The USB floppy is a Lacie branded floppy, connecting it to a working XP workstation shows it to be the Y-E Data USB floppy drive that is supposedly 100% compatible with XP per MS KB 916196.

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• How do I set up Grub properly to quad-boot Windows, Mac OS X, Linux, and FreeBSD?

  - by Joe

  Grub has gone completely insane on me. My quad-boot system was working great up until I upgraded Ubuntu to 12.04. Since Ubuntu overwrote the Grub stuff I had to repair it with my Mac OS X and FreeBSD entries. After this, trying to boot Mac OS X gave me the error "couldn't open file" and FreeBSD gave the error "no such partition". Windows and Ubuntu worked fine. So I tried repairing again because I figured something must've gone wrong in the install process. Then only Ubuntu would boot. Trying to boot Windows would give me the error "no argument specified". I tried repairing Grub once again, since I seemed to be getting different results each time. This time, Ubuntu no longer appeared in the Grub menu, and the errors for the other OSes were the same. So I booted into the Ubuntu 12.04 live CD and ran Boot-Repair with recommended settings. Now Grub is completely skipped and Windows boots up. I have absolutely no idea what is going on or why I get different results every time I reinstall Grub. Here is how my partitions are set up: sda1 - Storage drive, sdb1 - Windows, sdb2 - Mac OS X, sdb3 - FreeBSD, sdb4 - Extended, sdb5 - Ubuntu, sdb6 - Shared storage, sdb7 - Shared Storage, Here's my grub.cfg file: grub.cfg

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• NAS for Mac OS X Server

  - by SamAdmin

  I'm using Mac OS X Server and want to allow the users that connect to their network accounts to store their data on a NAS drive. I want the users to connect to the Lion server as this allows for better policies and management for me and for their afp share to be located on a NAS drive. I've looked into home directories and network logins however I don't want the users to connect into a different login environment, just an authentication against their provided account on the Lion server and for their finder to take them to their own storage area - located on the NAS drive. Currently I am using FreeNAS for both authentication and storage however there are getting to be far too many people to manage each afp share and account, plus just using FreeNAS is extremely limiting for expansion and if something goes wrong with 1 entity the entire system goes down. Using the Lion server for user accounts and policies will be much better for this expanding business. I have looked into LDAP, using the Lion server as an LDAP server to authenticate against for FreeNAS however I have had issues with this and thought a different approach could be better from the other side of the situation... Providing the account with somewhere to store data rather than the afp share authenticating against an LDAP server. I am wrong to try it this way? Is it possible to logically add storage to a Mac OS X Server which can be recognised as a local drive, so can be used for network accounts?

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• datagrid filter in c# using sql server

  - by malou17

  How to filter data in datagrid for example if u select the combo box in student number then input 1001 in the text field...all records in 1001 will appear in datagrid.....we are using sql server private void button2_Click(object sender, EventArgs e) { if (cbofilter.SelectedIndex == 0) { string sql; SqlConnection conn = new SqlConnection(); conn.ConnectionString = "Server= " + Environment.MachineName.ToString() + @"\; Initial Catalog=TEST;Integrated Security = true"; SqlDataAdapter da = new SqlDataAdapter(); DataSet ds1 = new DataSet(); ds1 = DBConn.getStudentDetails("sp_RetrieveSTUDNO"); sql = "Select * from Test where STUDNO like '" + txtvalue.Text + "'"; SqlCommand cmd = new SqlCommand(sql, conn); cmd.CommandType = CommandType.Text; da.SelectCommand = cmd; da.Fill(ds1); dbgStudentDetails.DataSource = ds1; dbgStudentDetails.DataMember = ds1.Tables[0].TableName; dbgStudentDetails.Refresh(); } else if (cbofilter.SelectedIndex == 1) { //string sql; //SqlConnection conn = new SqlConnection(); //conn.ConnectionString = "Server= " + Environment.MachineName.ToString() + @"\; Initial Catalog=TEST;Integrated Security = true"; //SqlDataAdapter da = new SqlDataAdapter(); //DataSet ds1 = new DataSet(); //ds1 = DBConn.getStudentDetails("sp_RetrieveSTUDNO"); //sql = "Select * from Test where Name like '" + txtvalue.Text + "'"; //SqlCommand cmd = new SqlCommand(sql,conn); //cmd.CommandType = CommandType.Text; //da.SelectCommand = cmd; //da.Fill(ds1); // dbgStudentDetails.DataSource = ds1; //dbgStudentDetails.DataMember = ds1.Tables[0].TableName; //ds.Tables[0].DefaultView.RowFilter = "Studno = + txtvalue.text + "; dbgStudentDetails.DataSource = ds.Tables[0]; dbgStudentDetails.Refresh(); } }

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• [Linq to SQL] Multiple foreign keys to the same table

  - by cdonner

  I have a reference table with all sorts of controlled value lookup data for gender, address type, contact type, etc. Many tables have multiple foreign keys to this reference table I also have many-to-many association tables that have two foreign keys to the same table. Unfortunately, when these tables are pulled into a Linq model and the DBML is generated, SQLMetal does not look at the names of the foreign key columns, or the names of the constraints, but only at the target table. So I end up with members called Reference1, Reference2, ... not very maintenance-friendly. Example: <Association Name="tb_reference_tb_account" Member="tb_reference" <====== ThisKey="shipping_preference_type_id" OtherKey="id" Type="tb_reference" IsForeignKey="true" /> <Association Name="tb_reference_tb_account1" Member="tb_reference1" <====== ThisKey="status_type_id" OtherKey="id" Type="tb_reference" IsForeignKey="true" /> I can go into the DBML and manually change the member names, of course, but this would mean I can no longer round-trip my database schema. This is not an option at the current stage of the model, which is still evolving. Splitting the reference table into n individual tables is also not desirable. I can probably write a script that runs against the XML after each generation and replaces the member name with something derived from ThisKey (since I adhere to a naming convention for these types of keys). Has anybody found a better solution to this problem?

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• Schema objects not visible in SQL Server Management Studio 2008

  - by Germ

  I'm experiencing a weird problem with a SQL login. When I connect to the server in Microsoft SQL Server Management Studio (2008) using this account, I cannot see any of the tables, stored procedures etc. that this account should have access to on a particular database. When I connect to the same server within Visual Studio (2008) with the same account everything is there. When I connect with the same account on a Virtual Machine everything is there. I've also had a co-worker connect to the server using the same login and he's able to view everything as well. I use Microsoft SQL Server Management Studio all day connecting to different servers and databases and I've never experienced this problem. Does anyone have any suggestions on how I can diagnose this problem? I've checked to make sure I don't have any Table filters etc. There's several database on this server and I'm able to see the correct tables that this account has access to in the other databases just fine. Running this query lists the tables I'm expecting to see. SELECT * FROM INFORMATION_SCHEMA.TABLES

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• Rails Fixtures Don't Seem to Support Transitive Associations

  - by Rick Wayne

  So I've got 3 models in my app, connected by HABTM relations: class Member < ActiveRecord::Base has_and_belongs_to_many :groups end class Group < ActiveRecord::Base has_and_belongs_to_many :software_instances end class SoftwareInstance < ActiveRecord::Base end And I have the appropriate join tables, and use foxy fixtures to load them: -- members.yml -- rick: name: Rick groups: cals -- groups.yml -- cals: name: CALS software_instances: delphi -- software_instances.yml -- delphi: name: No, this is not a joke, someone in our group is still maintaining Delphi apps... And I do a rake db:fixtures:load, and examine the tables. Yep, the join tables groups_members and groups_software_instances have appropriate IDs in, big numbers generated by hashing the fixture names. Yay! And if I run script/console, I can look at rick's groups and see that cals is in there, or cals's software_instances and delphi shows up. (Likewise delphi knows that it's in the group cals.) Yay! But if I look at rick.groups[0].software_instances...nada. []. And, oddly enough, rick.groups[0].id is something like 30 or 10, not 398398439. I've tried swapping around where the association is defined in the fixtures, e.g. -- members.yml -- rick name: rick -- groups.yml -- cals name: CALS members: rick No error, but same result. (Later: Confirmed, same behavior on MySQL. In fact I get the same thing if I take the foxification out and use ERB to directly create the join tables, so: -- license_groups_software_instances -- cals_delphi: group_id: <%= Fixtures.identify 'cals' % software_instance_id: <%= Fixtures.identify 'delphi' $ Before I chuck it all, reject foxy fixtures and all who sail in her and just hand-code IDs...anybody got a suggestion as to why this is happening? I'm currently working in Rails 2.3.2 with sqlite3, this occurs on both OS X and Ubuntu (and I think with MySQL too). TIA, my compadres.

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• OleDb database to DataSet and back in c#?

  - by Troy

  I'm writing a program that lets a user: Connect to an (arbitrary) View all of the tables in that database in separate DataGridViews Edit them in the program, generate random data, and see the results Choose to commit those changes or revert So I discovered the DataSet class, which looks like it's capable of holding everything that a database would, and I decided that the best thing to do here would be to load everything into one dataset, let the user edit it, and then save the dataset back to the database. The problem is that the only way I can find to load the database tables is this: set = new DataSet(); DataTable schema = connection.GetOleDbSchemaTable( OleDbSchemaGuid.Tables, new string[] { null, null, null, "TABLE" }); foreach (DataRow row in schema.Rows) { string tableName = row.Field<string>("TABLE_NAME"); DataTable dTable = new DataTable(); new OleDbDataAdapter("SELECT * FROM " + tableName, connection).Fill(dTable); dTable.TableName = tableName; set.Tables.Add(dTable); } while it seems like there should be a simpler way given that datasets appear to be designed for exactly this purpose. The real problem though is when I try saving these things. In order to use the OleDbDataAdapter.Update() method, I'm told that I have to provide valid INSERT queries. Doesn't that kind of negate the whole point of having a class to handle this stuff for me? Anyway, I'm hoping somebody can either explain how to load and save a database into a dataset or maybe give me a better idea of how to do what I'm trying to do. I could always parse the commands together myself, but that doesn't seem like the best solution.

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• PostgreSQL: Auto-partition a table

  - by Adam Matan

  Hi, I have a huge database which holds pairs of numbers (A,B), each ranging from 0 to 10,000 and stored as floats. e.g., (1, 9984.4), (2143.44, 124.243), (0.55, 0), ... Since the PostgreSQL table which stores these pairs grew quite large, I have decided to partition it into inheriting sub-tables. I intend to create 100 such tables, each storing a range of 1000x1000. The problem is that these numbers tend to come in large chunks of nearby numbers. It means that in the future, some tables will be nearly empty and some will hold a very large portion of the database. Unfortunately, the distribution of future pairs is yet unknown. I am looking for a way to automatically repartition my table. That means that if a certain subtable holds more than a specific number of pairs, it will be automatically partitioned into four sub-sub tables, and so on. My questions are: Is recursive partitioning and inheritance possible in PostgreSQL 8.3? Will indexes and query plans understand it? What's the best way to split a subtable once it grew too large? I should point out that this isn't a live database, so a downtime of few hours every week is totally acceptable. Thanks in advance, Adam

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• choosing row (from group) with max value in a SQL Server Database

  - by sriehl

  I have a large database and am putting together a report of the data. I have aggregated and summed the data from many tables to get two tables that look like the following. id | code | value id | code | value 13 | AA | 0.5 13 | AC | 2.0 13 | AB | 1.0 14 | AB | 1.5 14 | AA | 2.0 13 | AA | 0.5 15 | AB | 0.5 15 | AB | 3.0 15 | AD | 1.5 15 | AA | 1.0 I need to get a list of id's, with the code (sumed from both tables) with the largest value. 13 | AC 14 | AA 15 | AB There are 4-6 thousand records and it is not possible to change the original tables. I'm not too worried about performance as I only need to run it a few times a year. edit: Let me see if I can explain a bit more clearly, imagine the id is the customer id, the code is who they ordered from and the value is how much they spent there. I need a list of the all the customer id's and the store that customer spent the most money at (and if they spent the same at two different stores, put a value such as 'ZZ' in for the store name).

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• Product Catalog Schema design

  - by FlySwat

  I'm building a proof of concept schema for a product catalog to possibly replace a very aging and crufty one we use. In our business, we sell both physical materials and services (one time and reoccurring charges). The current catalog schema has each distinct category broken out into individual tables, while this is nicely normalized and performs well, it is fairly difficult to extend. Adding a new attribute to a particular product involves changing the table schema and backpopulating old data. An idea I've been toying with has been something along the line of a base set of entity tables in 3rd normal form, these will contain the facts that are common among ALL products. Then, I'd like to build an Attribute-Entity-Value schema that allows each entity type to be extended in a flexible way using just data and no schema changes. Finally, I'd like to denormalize this data model into materialized views for each individual entity type. This views are what the application would access. We also have many tables that contain business rules and compatibility rules. These would join against the base entity tables instead of the views. My big concerns here are: Performance - Attribute-Entity-Value schemas are flexible, but typically perform poorly, should I be concerned? More Performance - Denormalizing using materialized views may have some risks, I'm not positive on this yet. Complexity - While this schema is flexible and maintainable using just data, I worry that the complexity of the design might make future schema changes difficult. For those who have designed product catalogs for large scale enterprises, am I going down the totally wrong path? Is there any good best practice schema design reading available for product catalogs?

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• NoSuchMethodError in Java using XStream

  - by Brad Germain

  I'm trying to save a database into a file using XStream and then open it again later using XStream and deserialize it back into the objects it was in previously. The database consists of an arraylist of tables, which consists of an arraylist of a data class where the data class contains an arraylist of objects. I'm basically trying to create an sql compiler. I'm currently getting a java.lang.NoSuchMethodError because of the last line in the load method. Here's what I have: Save Method public void save(Database DB){ File file = new File(DB.getName().toUpperCase() + ".xml"); //Test sample DB.createTable("TBL1(character(a));"); DB.tables.getTable("TBL1").rows.add(new DataList()); DB.tables.getTable("TBL1").rows.getRow(0).add(10); XStream xstream = new XStream(); //Database xstream.alias("Database", Database.class); //Tables xstream.alias("Table", Table.class); //Rows xstream.alias("Row", DataList.class); //Data //xstream.alias("Data", Object.class); //String xml = xstream.toXML(DB); Writer writer = null; try { writer = new FileWriter(file); writer.write(xstream.toXML(DB)); writer.close(); } catch (IOException e) { e.printStackTrace(); } } Load Method public void Load(String dbName){ XStream xstream = new XStream(); BufferedReader br; StringBuffer buff = null; try { br = new BufferedReader(new FileReader(dbName + ".xml")); buff = new StringBuffer(); String line; while((line = br.readLine()) != null){ buff.append(line); } } catch (FileNotFoundException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } database = (Database)xstream.fromXML(buff.toString()); }

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• How can I stop an auto-generated Linq to SQL class from loading ALL data?

  - by Gary McGill

  I have an ASP.NET MVC project, much like the NerdDinner tutorial example. (I'm using MVC 2, but followed the NerdDinner tutorial in order to create it). As per the instructions in part 3 of the tutorial, I've created a Linq-to-SQL model of my database by creating a "Linq to SQL Classes" (.dbml) surface, and dropping my database tables onto it. The designer has automatically added relationships between the generated classes based on my database tables. Let's say that my classes are as per the NerdDinner example, so I have Dinner and RSVP tables, where each Dinner record is associated with many RSVP records - hence in the generated classes, the Dinner object has a RSVPs property which is a list of RSVP objects. My problem is this: it appears (and I'd be gladly proved wrong on this) that as soon as I access a Dinner object, it's loading all of the corresponding RSVP objects, even if I don't use the RSVPs member. First question: is this really the default behavior for the generated classes? In my particular situation, the object graph contains many more tables (which have an order of magnitude more records), and so this is disastrous behaviour - I'd be loading tons of data when all I want to do is show the details of a single parent record. Second question: are there any properties exposed through the designer UI that would let me modify this behavior? (I can't find any). Third question: I've seen a description of how to control the loading of related records in a DataContext by using a DataShape object associated with the DataContext. Is that what I'm meant to do, and if so are there any tutorials like the NerdDinner one that would show not only how to do it, but also suggest a 'pattern' for normal use?

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• How can I stop an auto-generated Linq to SQL class from loading ALL data?

  - by Gary McGill

  DUPLICATE of http://stackoverflow.com/questions/2433422/how-can-i-stop-an-auto-generated-linq-to-sql-class-from-loading-all-data post answers there! I have an ASP.NET MVC project, much like the NerdDinner tutorial example. (I'm using MVC 2, but followed the NerdDinner tutorial in order to create it). As per the instructions in part 3 of the tutorial, I've created a Linq-to-SQL model of my database by creating a "Linq to SQL Classes" (.dbml) surface, and dropping my database tables onto it. The designer has automatically added relationships between the generated classes based on my database tables. Let's say that my classes are as per the NerdDinner example, so I have Dinner and RSVP tables, where each Dinner record is associated with many RSVP records - hence in the generated classes, the Dinner object has a RSVPs property which is a list of RSVP objects. My problem is this: it appears (and I'd be gladly proved wrong on this) that as soon as I access a Dinner object, it's loading all of the corresponding RSVP objects, even if I don't use the RSVPs member. First question: is this really the default behavior for the generated classes? In my particular situation, the object graph contains many more tables (which have an order of magnitude more records), and so this is disastrous behaviour - I'd be loading tons of data when all I want to do is show the details of a single parent record. Second question: are there any properties exposed through the designer UI that would let me modify this behavior? (I can't find any). Third question: I've seen a description of how to control the loading of related records in a DataContext by using a DataShape object associated with the DataContext. Is that what I'm meant to do, and if so are there any tutorials like the NerdDinner one that would show not only how to do it, but also suggest a 'pattern' for normal use?

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• Doing large updates against indexed view

  - by user217136

  We have an indexed view that runs across three large tables. Two of these tables (A & B) are constantly getting updated with user transactions and the other table (C) contains data product info that is needs to be updated once a week. This product table contains over 6 million records. We need this view across these three tables for our core business process and unfortunately we cannot change this aspect. We even had a sql server MVP come in to help test under load to make sure we have the most efficient configuration. There is one column in the product table that gets utilized in the view and has to be updated each week. The problem we are now encountering is that as volume is increasing on our transactions against tables A & B, the update to Table C is causing deadlocks. I have tried several different methods to no avail: 1) I was hoping that we could change the view so that table C could be a dirty read "WITH (NOLOCK)" but apparently that functionality is not available with indexes views. 2) I thought about updating a new column in Table C and then just renaming it when the process is done but you cannot do that due to the dependency in the view. 3) I also entertained the idea of writing this value to a temporary product table, and then running an ALTER statement against the view to have it point to my new table. however when i did that the indexes on my view were dropped and it took quite a bit of time to recreate them. 4) we tried to do the weekly update in small chunks (as small as 100 records at a time) but we still run into dead locks. questions: a) we are using sql server 2005. Does sql server 2008 have a new functionality with their indexed views that would help us? Is there now a way to do dirty reads w/ an indexed view? b) a better approach to altering an existing view to point to a new table? thanks!

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• WPF Toolkit: Nullable object must have a value

  - by Via Lactea

  Hi All, I am trying to create some line charts from a dataset and getting an error (WPF+WPF Toolkit + C#): Nullable object must have a value Here is a code that I use to add some data points to the chart: ObservableCollection points = new ObservableCollection(); foreach (DataRow dr in dc.Tables[0].Rows) { points.Add(new VelChartPoint() { Label = dr[0].ToString(), Value = double.Parse(dr[1].ToString()) }); } Here is a class VelChartPoint public class VelChartPoint : VelObject, INotifyPropertyChanged { public DateTime Date { get; set; } public string Label { get; set; } private double _Value; public double Value { get { return _Value; } set { _Value = value; var handler = PropertyChanged; if (null != handler) { handler.Invoke(this, new PropertyChangedEventArgs("Value")); } } } public string FieldName { get; set; } public event PropertyChangedEventHandler PropertyChanged; public VelChartPoint() { } } So the problem occures in this part of the code points.Add(new VelChartPoint { Name = dc.Tables[0].Rows[0][0].ToString(), Value = double.Parse(dc.Tables[0].Rows[0][1].ToString()) } ); I've made some tests, here are some results i've found out. This part of code does'nt work for me: string[] labels = new string[] { "label1", "label2", "label3" }; foreach (string label in labels) { points.Add(new VelChartPoint { Name = label, Value = 500.0 } ); } But this one works fine: points.Add(new VelChartPoint { Name = "LabelText", Value = double.Parse(dc.Tables[0].Rows[0][1].ToString()) } ); Please, help me to solve this error.

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• SQL GUID Vs Integer

  - by Dal

  Hi I have recently started a new job and noticed that all the SQL tables use the GUID data type for the primary key. In my previous job we used integers (Auto-Increment) for the primary key and it was a lot more easier to work with in my opinion. For example, say you had two related tables; Product and ProductType - I could easily cross check the 'ProductTypeID' column of both tables for a particular row to quickly map the data in my head because its easy to store the number (2,4,45 etc) as opposed to (E75B92A3-3299-4407-A913-C5CA196B3CAB). The extra frustration comes from me wanting to understand how the tables are related, sadly there is no Database diagram :( A lot of people say that GUID's are better because you can define the unique identifer in your C# code for example using NewID() without requiring SQL SERVER to do it - this also allows you to know provisionally what the ID will be.... but I've seen that it is possible to still retrieve the 'next auto-incremented integer' too. A DBA contractor reported that our queries could be up to 30% faster if we used the Integer type instead of GUIDS... Why does the GUID data type exist, what advantages does it really provide?... Even if its a choice by some professional there must be some good reasons as to why its implemented?

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