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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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• J2ME cache issue

  - by kiennt

  I have to write a J2ME app to retrieve images from server and display in mobile phone. I have seen and test that Snaptu have a mechanism to cache image, event with 100 images (both normal size and zoom size). I wonder how they can do that? I though that those guys use rms to save image stream to data. But when i check in working folder of simulater( I use Windows XP and Sun Wireless Toolkit 3.0, the Emulator device i use to run my program is CLDC Device 1 - my working folder is C:\Document And Settings\Administrator\javame-sdk\3.0\work\6\appdb), i see some .db file. When i delete these files, i still can view cache image in my emulator???? I also thought that those guys use heap memory to save image. But it is not correct because when i set limit device memory is 2MB (like some mobile phones), and i load and view 100 images in zoom size, it didn't make OutOfMemory Error? It so weird. Any one can help me? Thanks

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• Why does stored procedure invalidate SQL Cache Dependency?

  - by Fabio Milheiro

  After many hours, I finally realize that I am working correctly with the Cache object in my ASP.NET application but my stored procedures stops it from working correctly. This stored procedure works correctly: CREATE PROCEDURE [dbo].[ListLanguages] @Page INT = 1, @ItemsPerPage INT = 10, @OrderBy NVARCHAR (100) = 'ID', @OrderDirection NVARCHAR(4) = 'DESC' AS BEGIN SELECT ID, [Name], Flag, IsDefault FROM dbo.Languages END But this (the one I wanted) doesn't: CREATE PROCEDURE [dbo].[ListLanguages] @Page INT = 1, @ItemsPerPage INT = 10, @OrderBy NVARCHAR (100) = 'ID', @OrderDirection NVARCHAR(4) = 'DESC', @TotalRecords INT OUTPUT AS BEGIN SET @TotalRecords = 10 EXEC('SELECT ID, Name, Flag, IsDefault FROM ( SELECT ROW_NUMBER() OVER (ORDER BY ' + @OrderBy + ' ' + @OrderDirection + ') as Row, ID, Name, Flag, IsDefault FROM dbo.Languages) results WHERE Row BETWEEN ((' + @Page + '-1)*' + @ItemsPerPage + '+1) AND (' + @Page + '*' + @ItemsPerPage + ')') END I gave the @TotalRecords parameter the value 10 so you can be sure that the problem is not from the COUNT(*) function which I know is not supported well. Also, when I run it from SQL Server Management Studio, it does exactly what it should do. In the ASP.NET application the results are retrieved correctly, only the cache is somehow unable to work! Can you please help? Maybe a hint I believe that the reason why the dependency HasChanged property is related to the fact that the column Row generated from the ROW_NUMBER is only temporary and, therefore, the SQL SERVER is not able to to say whether the results are changed or not. That's why HasChanged is always set to true. Does anyone know how to paginate results from SQL SERVER without using COUNT or ROW_NUMBER functions?

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• Cache data in SQL CE database

  - by user93422

  Background I have an SQL CE database, that is constantly updated (every second). I have a (web) application that allows a user to look at the data in real-time. At some point a user can click "take a snapshot" button, and it will open the snapshot in a different window. And then on that form, there is "print" and "download" buttons that will either generate a page for printing, or will stream the data as CSV file - but same data snapshot has to be used, i.e. I can't go to the DB to get latest data for that. Details SQL CE dabatase is exposed through WCF web service. Snapshot consists of up to 500 records, 10 columns each. Expiration time on the snapshot of 2 hours is sufficient. It is a low-traffic application, so I don't expect more than few (5) connections at the same time. Loosing snapshot is not a big deal, user can simply generate new one. database is accessed by self-hosted WCF web service using Linq-to-SQL. Web site is ASP.NET MVC hosted on UltiDev Cassini. database, and web site are most likely be on the same box, when deployed. The entire app is intranet bound. Problem I need to cache the snapshot of the data at the moment user pressed "take a snapshot" button, so that I can use same data to generate print page, or generate a file for download. Solution 1: Each time there is a need to generate a snapshot, I will create a table in the database. Since there are no temp tables in SQL CE, I will need to clean it up myself. Solution 2: Cache the snapshot in-memory on either DB server, or web server. Question: Is there anything wrong with proposed solutions? Any different solution suggestions?

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• Flex 3 - Image cache

  - by BS_C3

  Hello Community. I'm doing an Image Cache following this method: http://www.brandondement.com/blog/2009/08/18/creating-an-image-cache-with-actionscript-3/ I copied the two as classes, renaming them CachedImage and CachedImageMap. The thing is that I don't want to store the image after being loaded a first time, but while the application is being loaded. For that, I've created a function that is called by the application pre-initialize event. This is how it looks: private function loadImages():void { var im:CachedImage = new CachedImage; var sources:ArrayCollection = new ArrayCollection; for each(var cs in divisionData.division.collections.collection.collectionSelection) { sources.addItem(cs.toString()); } for each(var se in divisionData.division.collections.collection.searchEngine) { sources.addItem(se.toString()); } for each( var source:String in sources) { im.source = source; im.load(source); } } The sources are properly retrieved. However, even if I use the load method, I do not get the "complete" event... As if the image is not being loaded... How is that? Any help would be appreciated. Thanks in advance. Regards, BS_C3

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• Cakephp cache only caching one file per action

  - by Jamesz

  Hi, I have a songs controller. Within the songs controller i have a 'view' action which get's passed an id, eg /songs/view/1 /songs/view/5 /songs/view/500 When a user visits /songs/view/1, the file is cached correctly and saved as 'songs_view_1.php' Now for the problem, when a user hit's a different song, eg /songs/view/2, the 'songs_view_1.php' is deleted and '/songs/view/2.php' is in it's place. The cahced files will stay there for a day if I don't visit a different url, and visiting a different action will not affect any other action's cached file. I've tried replacing my 'cake' folder (from 1.2 to 1.2.6), but that didn't do anything. I get no error messages at all and nothing in the logs. Here's my code, I've tried umpteen variations all ending up with the same problem. var $helpers = array('Cache'); var $cacheAction = array( 'view/' => '+1 day' ); Any ideas? EDIT: After some more testing, this code var $cacheAction = array( 'view/1' => "1 day", 'view/2' => "1 day" ); will cache 'view/1' or 'view/2', but delete the previous page as before. If I visit '/view/3' it will delete the cached page from before... sigh EDIT: Having the same issue on another server with same code...

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• Turn A Flash Drive Into a Portable Web Server

  - by Matthew Guay

  Portable applications are very useful for getting work done on the go, but how about portable servers?  Here’s how you can turn your flash drive into a portable web server. Getting Started To put a full web server on our flash drive, we’re going to use XAMPP Lite.  This lightweight, preconfigured server includes recent versions of Apache, MySQL, and PHP so you can run most websites and webapps directly from it.  You could use the full XAMPP, which includes more features such as a FileZilla FTP server and OpenSSL, but for most purposes, the light version is plenty for a portable server. Download the latest version of XAMPP Lite (link below).  In this tutorial, we used the self-extracting EXE version; you could choose the ZIP file and extract the files yourself, but we found it easier to use the executable. Run the installer, and click Browse choose where to install your server. Select your flash drive, or a folder in it, and click Ok.  Make sure your flash drive has at least 250MB of available storage space.  XAMPP will create an xampplite folder and store all the files in it during the installation.   Click Install, and all of the files will be extracted to your flash drive.  This may take a few moments depending on your flash drive’s speed. When the extraction process is finished, a Command Prompt window will open to finish the installation.  The first prompt will ask if you want to add shortcuts to the start menu and desktop; enter “n” since we don’t want to create start menu links to our portable server. Now enter “y” to configure XAMPP’s directories automatically. Finally, enter “y” to make XAMPP fully portable.  It will set up the servers to run without specific drive letters so your server will run from any computer. XAMPP will finalize your changes; press Enter when everything is completed. Setup will automatically launch the command line version of XAMPP.  On first run, confirm that your time zone is correct. And that’s it!  You can now run XAMPP’s control panel by entering 1, or you can exit and run XAMPP from any other computer with your flash drive. To complete your portable webserver kit, you may want to install Portable Firefox or Iron Browser on your flash drive so you always have your favorite browser ready to use. Running your portable server Using your portable server is very simple.  Open the xampplite folder on your flash drive and launch xampp-control.exe. Click Start beside Apache and MySql to get your webserver running. Please note: Do not check the Svc box, as this will run the server as a Windows service.  To keep XAMPP portable, you do not want it running as a service! Windows Firewall may prompt you that it blocked the server; click Allow access to let your server run. Once they’re running, you can click Admin to open the default XAMPP admin page running from your local webserver.  Or, you can view it by browsing to http://localhost/ or http://127.0.0.1/ in your browser. If everything is working correctly, you should see this page in your browser.  Choose your default language… And then you’ll see the default XAMPP admin page.   Click the Status link on the left sidebar to make sure everything is running correctly. If you click the Admin button for MySql in the XAMPP Control Panel, it will open phpMyAdmin in your default browser.  Alternately, you can open the MySql admin page by entering http://localhost/phpmyadmin/ or http://127.0.0.1/phpmyadmin/ in your favorite browser. Now you can add your own webpages to your webserver.  Save all of your web files in the \xampplight\htdocs\ folder on your flash drive. Install WordPress in your portable server Since XAMPP Lite includes MySql and PHP, you can even run webapps such as WordPress, the popular CMS and blogging platform.  Download WordPress (link below), and extract the files to the \xampplite\htdocs folder on your flash drive. Now all of the WordPress files are stored in \xampplite\htdocs\wordpress on your flash drive. We still need to setup WordPress on our portable server.  Open your MySql admin page http://localhost/phpmyadmin/ to create a new database for WordPress.  Enter a name for your database in the “Create new database” box, and click Create. Click the Privileges tab on the top, and the select “Add a new User”.   Enter a username and password for the database, and then click the Go button on the bottom of the page. Using WordPress Now, in your browser, enter http://localhost/wordpress/wp-admin/install.php.  Click Create a Configuration File to continue. Make sure you have your Database name, username, and password we created previously, and click “Let’s Go!” Enter your WordPress database name, username, and password, leave the other two entries as default, and click Submit. You should now have the database all ready to go.  Click “Run the install” to finish installing WordPress. Enter a title, username, and password for your test blog, as well as your email address, and then click “Install WordPress”. You now have a portable install of WordPress.  Click “Log In” to  access your WordPress admin page. Enter your username and password, and click Log In. Here you can add pages, posts, themes, extensions, and anything else just like you would on a normal WordPress site.  This is a great way to experiment with WordPress without messing up your real website. You can view your portable WordPress site by entering http://localhost/wordpress/ in your address bar. Closing your server When you’re done running your test server, click the Stop button on each of the services and then click the Exit button in the XAMPP control panel.  If you press the exit button on the top of the window, it will just minimize the control panel to the tray.   Alternately, you can shutdown your server by running xampp_stop.exe from your xampplite folder. Conclusion XAMPP Lite gives you a great way to run a full webserver directly from your flash drive.  Now, anywhere you go, you can test and tweak your webpages and webapps from any Windows computer.  Links Download XAMPP Lite Download WordPress Similar Articles Productive Geek Tips BitLocker To Go Encrypts Portable Flash Drives in Windows 7How To Use BitLocker on Drives without TPMSpeed up Your Windows Vista Computer with ReadyBoostView and Manage Flash Cookies the Easy WayInstall and Run Applications from Your iPod, Flash Drive or Mp3 Player TouchFreeze Alternative in AutoHotkey The Icy Undertow Desktop Windows Home Server – Backup to LAN The Clear & Clean Desktop Use This Bookmarklet to Easily Get Albums Use AutoHotkey to Assign a Hotkey to a Specific Window Latest Software Reviews Tinyhacker Random Tips DVDFab 6 Revo Uninstaller Pro Registry Mechanic 9 for Windows PC Tools Internet Security Suite 2010 OutlookStatView Scans and Displays General Usage Statistics How to Add Exceptions to the Windows Firewall Office 2010 reviewed in depth by Ed Bott FoxClocks adds World Times in your Statusbar (Firefox) Have Fun Editing Photo Editing with Citrify Outlook Connector Upgrade Error

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• DVD-RW Drive not recognizing a DVD+R disc

  - by unknown (yahoo)

  Hi everyone, I am having trouble burning DVD+R disc's. My OS is vista and i have used this burner and these same discs in the past. I haven't had the need to do so in months and now that i come back to create some backups my DVD/RW drive doesn't recognize a brand new DVD+R disc. These disc are the same ones i have used in the past(Same Pack even). Anyone have any idea what this might be. Maybe a vista upgrade or something that i downloaded in the last few months that could have thrown something off? Thanks in advance.

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• 6 Ways to Free Up Hard Drive Space Used by Windows System Files

  - by Chris Hoffman

  We’ve previously covered the standard ways to free up space on Windows. But if you have a small solid-state drive and really want more hard space, there are geekier ways to reclaim hard drive space. Not all of these tips are recommended — in fact, if you have more than enough hard drive space, following these tips may actually be a bad idea. There’s a tradeoff to changing all of these settings. Erase Windows Update Uninstall Files Windows allows you to uninstall patches you install from Windows Update. This is helpful if an update ever causes a problem — but how often do you need to uninstall an update, anyway? And will you really ever need to uninstall updates you’ve installed several years ago? These uninstall files are probably just wasting space on your hard drive. A recent update released for Windows 7 allows you to erase Windows Update files from the Windows Disk Cleanup tool. Open Disk Cleanup, click Clean up system files, check the Windows Update Cleanup option, and click OK. If you don’t see this option, run Windows Update and install the available updates. Remove the Recovery Partition Windows computers generally come with recovery partitions that allow you to reset your computer back to its factory default state without juggling discs. The recovery partition allows you to reinstall Windows or use the Refresh and Reset your PC features. These partitions take up a lot of space as they need to contain a complete system image. On Microsoft’s Surface Pro, the recovery partition takes up about 8-10 GB. On other computers, it may be even larger as it needs to contain all the bloatware the manufacturer included. Windows 8 makes it easy to copy the recovery partition to removable media and remove it from your hard drive. If you do this, you’ll need to insert the removable media whenever you want to refresh or reset your PC. On older Windows 7 computers, you could delete the recovery partition using a partition manager — but ensure you have recovery media ready if you ever need to install Windows. If you prefer to install Windows from scratch instead of using your manufacturer’s recovery partition, you can just insert a standard Window disc if you ever want to reinstall Windows. Disable the Hibernation File Windows creates a hidden hibernation file at C:\hiberfil.sys. Whenever you hibernate the computer, Windows saves the contents of your RAM to the hibernation file and shuts down the computer. When it boots up again, it reads the contents of the file into memory and restores your computer to the state it was in. As this file needs to contain much of the contents of your RAM, it’s 75% of the size of your installed RAM. If you have 12 GB of memory, that means this file takes about 9 GB of space. On a laptop, you probably don’t want to disable hibernation. However, if you have a desktop with a small solid-state drive, you may want to disable hibernation to recover the space. When you disable hibernation, Windows will delete the hibernation file. You can’t move this file off the system drive, as it needs to be on C:\ so Windows can read it at boot. Note that this file and the paging file are marked as “protected operating system files” and aren’t visible by default. Shrink the Paging File The Windows paging file, also known as the page file, is a file Windows uses if your computer’s available RAM ever fills up. Windows will then “page out” data to disk, ensuring there’s always available memory for applications — even if there isn’t enough physical RAM. The paging file is located at C:\pagefile.sys by default. You can shrink it or disable it if you’re really crunched for space, but we don’t recommend disabling it as that can cause problems if your computer ever needs some paging space. On our computer with 12 GB of RAM, the paging file takes up 12 GB of hard drive space by default. If you have a lot of RAM, you can certainly decrease the size — we’d probably be fine with 2 GB or even less. However, this depends on the programs you use and how much memory they require. The paging file can also be moved to another drive — for example, you could move it from a small SSD to a slower, larger hard drive. It will be slower if Windows ever needs to use the paging file, but it won’t use important SSD space. Configure System Restore Windows seems to use about 10 GB of hard drive space for “System Protection” by default. This space is used for System Restore snapshots, allowing you to restore previous versions of system files if you ever run into a system problem. If you need to free up space, you could reduce the amount of space allocated to system restore or even disable it entirely. Of course, if you disable it entirely, you’ll be unable to use system restore if you ever need it. You’d have to reinstall Windows, perform a Refresh or Reset, or fix any problems manually. Tweak Your Windows Installer Disc Want to really start stripping down Windows, ripping out components that are installed by default? You can do this with a tool designed for modifying Windows installer discs, such as WinReducer for Windows 8 or RT Se7en Lite for Windows 7. These tools allow you to create a customized installation disc, slipstreaming in updates and configuring default options. You can also use them to remove components from the Windows disc, shrinking the size of the resulting Windows installation. This isn’t recommended as you could cause problems with your Windows installation by removing important features. But it’s certainly an option if you want to make Windows as tiny as possible. Most Windows users can benefit from removing Windows Update uninstallation files, so it’s good to see that Microsoft finally gave Windows 7 users the ability to quickly and easily erase these files. However, if you have more than enough hard drive space, you should probably leave well enough alone and let Windows manage the rest of these settings on its own. Image Credit: Yutaka Tsutano on Flickr     

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• jump to page of a pdf in google docs / drive / apps

  - by Aaron - Solution Evangelist

  i want to jump to a specific page of a pdf file via the google docs via the editor url https://docs.google.com/file/d/xxx/edit or the embed url https://docs.google.com/file/d/xxx/preview i am not looking to use the http://docs.google.com/gview?url= referenced in the stackoverflow question how to open specific page on Google's docs viewer as i want to do this for documents where authentication is required the the document is not available via public url. is there some way of appending an anchor (i would have expected it to be https://docs.google.com/file/d/xxx/preview#10) or a query (e.g. https://docs.google.com/file/d/xxx/preview?page=10) to the google docs / drive / apps viewer?

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• Windows XP loses drive letter for existing partition on disk

  - by Kev

  Hi, apologies if this has already been asked - I couldn't spot anything exactly the same. I'm looking for help on the fact that Windows XP has suddenly decided to stop assigning a drive letter to the second partition on my laptop's disk. I haven't added or changed hardware and I keep everything pretty clean in terms of software installed. I've partitioned the disk into a system partition on C: and a user partition on d: but lately, when booting or coming out of hibernation or sometime from stand-by, Windows will lose it's d: mapping. If I notice and remap it from MMC, everything will be perfectly happy and will keep going. Any help on this will be greatly appreciated. Cheers, Kev

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• User's home drive permissions don't contain system or administrators on Windows Server 2008 R2

  - by JohnyV

  I have a user whose home drive has only that user in the permissions. No administrators, etc. I have tried to take ownership as a local administrator however I cant seem to apply settings to the child objects -- it still gives me a permission denied error. I know there are some handy CLI utils that can redo permissions. Any ideas? Or even a way to do it through Windows? The file server is a 2008 R2 server.

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• Cost Comparison Hard Disk Drive to Solid State Drive on Price per Gigabyte - dispelling a myth!

  - by tonyrogerson

  It is often said that Hard Disk Drive storage is significantly cheaper per GiByte than Solid State Devices – this is wholly inaccurate within the database space. People need to look at the cost of the complete solution and not just a single component part in isolation to what is really required to meet the business requirement. Buying a single Hitachi Ultrastar 600GB 3.5” SAS 15Krpm hard disk drive will cost approximately £239.60 (http://scan.co.uk, 22nd March 2012) compared to an OCZ 600GB Z-Drive R4 CM84 PCIe costing £2,316.54 (http://scan.co.uk, 22nd March 2012); I’ve not included FusionIO ioDrive because there is no public pricing available for it – something I never understand and personally when companies do this I immediately think what are they hiding, luckily in FusionIO’s case the product is proven though is expensive compared to OCZ enterprise offerings. On the face of it the single 15Krpm hard disk has a price per GB of £0.39, the SSD £3.86; this is what you will see in the press and this is what sales people will use in comparing the two technologies – do not be fooled by this bullshit people! What is the requirement? The requirement is the database will have a static size of 400GB kept static through archiving so growth and trim will balance the database size, the client requires resilience, there will be several hundred call centre staff querying the database where queries will read a small amount of data but there will be no hot spot in the data so the randomness will come across the entire 400GB of the database, estimates predict that the IOps required will be approximately 4,000IOps at peak times, because it’s a call centre system the IO latency is important and must remain below 5ms per IO. The balance between read and write is 70% read, 30% write. The requirement is now defined and we have three of the most important pieces of the puzzle – space required, estimated IOps and maximum latency per IO. Something to consider with regard SQL Server; write activity requires synchronous IO to the storage media specifically the transaction log; that means the write thread will wait until the IO is completed and hardened off until the thread can continue execution, the requirement has stated that 30% of the system activity will be write so we can expect a high amount of synchronous activity. The hardware solution needs to be defined; two possible solutions: hard disk or solid state based; the real question now is how many hard disks are required to achieve the IO throughput, the latency and resilience, ditto for the solid state. Hard Drive solution On a test on an HP DL380, P410i controller using IOMeter against a single 15Krpm 146GB SAS drive, the throughput given on a transfer size of 8KiB against a 40GiB file on a freshly formatted disk where the partition is the only partition on the disk thus the 40GiB file is on the outer edge of the drive so more sectors can be read before head movement is required: For 100% sequential IO at a queue depth of 16 with 8 worker threads 43,537 IOps at an average latency of 2.93ms (340 MiB/s), for 100% random IO at the same queue depth and worker threads 3,733 IOps at an average latency of 34.06ms (34 MiB/s). The same test was done on the same disk but the test file was 130GiB: For 100% sequential IO at a queue depth of 16 with 8 worker threads 43,537 IOps at an average latency of 2.93ms (340 MiB/s), for 100% random IO at the same queue depth and worker threads 528 IOps at an average latency of 217.49ms (4 MiB/s). From the result it is clear random performance gets worse as the disk fills up – I’m currently writing an article on short stroking which will cover this in detail. Given the work load is random in nature looking at the random performance of the single drive when only 40 GiB of the 146 GB is used gives near the IOps required but the latency is way out. Luckily I have tested 6 x 15Krpm 146GB SAS 15Krpm drives in a RAID 0 using the same test methodology, for the same test above on a 130 GiB for each drive added the performance boost is near linear, for each drive added throughput goes up by 5 MiB/sec, IOps by 700 IOps and latency reducing nearly 50% per drive added (172 ms, 94 ms, 65 ms, 47 ms, 37 ms, 30 ms). This is because the same 130GiB is spread out more as you add drives 130 / 1, 130 / 2, 130 / 3 etc. so implicit short stroking is occurring because there is less file on each drive so less head movement required. The best latency is still 30 ms but we have the IOps required now, but that’s on a 130GiB file and not the 400GiB we need. Some reality check here: a) the drive randomness is more likely to be 50/50 and not a full 100% but the above has highlighted the effect randomness has on the drive and the more a drive fills with data the worse the effect. For argument sake let us assume that for the given workload we need 8 disks to do the job, for resilience reasons we will need 16 because we need to RAID 1+0 them in order to get the throughput and the resilience, RAID 5 would degrade performance. Cost for hard drives: 16 x £239.60 = £3,833.60 For the hard drives we will need disk controllers and a separate external disk array because the likelihood is that the server itself won’t take the drives, a quick spec off DELL for a PowerVault MD1220 which gives the dual pathing with 16 disks 146GB 15Krpm 2.5” disks is priced at £7,438.00, note its probably more once we had two controller cards to sit in the server in, racking etc. Minimum cost taking the DELL quote as an example is therefore: {Cost of Hardware} / {Storage Required} £7,438.60 / 400 = £18.595 per GB £18.59 per GiB is a far cry from the £0.39 we had been told by the salesman and the myth. Yes, the storage array is composed of 16 x 146 disks in RAID 10 (therefore 8 usable) giving an effective usable storage availability of 1168GB but the actual storage requirement is only 400 and the extra disks have had to be purchased to get the  IOps up. Solid State Drive solution A single card significantly exceeds the IOps and latency required, for resilience two will be required. ( £2,316.54 * 2 ) / 400 = £11.58 per GB With the SSD solution only two PCIe sockets are required, no external disk units, no additional controllers, no redundant controllers etc. Conclusion I hope by showing you an example that the myth that hard disk drives are cheaper per GiB than Solid State has now been dispelled - £11.58 per GB for SSD compared to £18.59 for Hard Disk. I’ve not even touched on the running costs, compare the costs of running 18 hard disks, that’s a lot of heat and power compared to two PCIe cards!Just a quick note: I've left a fair amount of information out due to this being a blog! If in doubt, email me :)I'll also deal with the myth that SSD's wear out at a later date as well - that's just way over done still, yes, 5 years ago, but now - no.

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• Refresh devices - reconnect CF card drive by script (unplug-plug equivalent)

  - by Chris

  Hello I plug a completely clean CF-card into my USB card-writer. Then I dd a mbr block of 512 bytes size to the device, which contains the partition table and the definition of one partition. Problem: While "fdisk -l /dev/sdx" correctly displays the partition, it happens that there is no device like "/dev/sdx1" after these operations (as it was not present before). Unplugging and plugging the card-writer solves the problem and makes the device(s) appear. Since I use this procedure in a script, manually unplugging and re-plugging is no option whatsoever. Is there a way to "refresh" the devices or to "unplug and re-plug" the drive by script such that /dev/sdx1 appears? Thanks for any help, Chris

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• Repair snapped USB flash drive

  - by Richard Slater

  I have a USB Flash Drive that has had the USB connector snapped away from the circuit board. In the past I have had great sucess with soldering the connector back to the circuit board with 4 solid core wires. Unfortunatly this particular device shows up as "Unknown Device" in device manager and displays 0ma power usage. Giving a closer look at the circuit board it appears that the Data + connector has come away from the PCB. Which would explain why it is not recognised. Is there any practicable way of lifting the data from the device? larger version

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• If Ubuntu freezes when running off a USB drive, will it freeze after full installation?

  - by fearoffours

  I'm planning to install Ubuntu on an aging Compaq Presario V5000. I've established that the Unity desktop is not suited to this laptop, and am now using the standard (Gnome?) desktop. I'm grappling with ndiswrapper and my wireless chipset. But I'm still running it off a USB drive before I take the plunge and install properly to my internal HD. Part of my reticence in completing the installation is I'm experience freezes after about 10-20 minutes usage. Is this likely to be in any way related to running it off the USB drive?

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• Nginx Reverse Proxy : post_action if proxy cache hit - Possbile?

  - by anonymous-one

  We have recently found out about nginxes post_action. We were wondering it there was a way to use this directive if a proxy cache hit is made? The flow we were hoping on is as follows: 1) User request comes in 2) If cache HIT goto A / If cache MISS goto B A) 1) Serve Cached Result A) 2) post_action to another url on the backend B) 1) Server request from backend B) 2) Store result from backend Any ideas if this is possible via post_action? Thanks!

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• How do I safely use a virus infected USB drive in Ubuntu?

  - by suhridk

  I have an USB drive which I know is virus infected (an anti-virus on my friend's machine detected it). Unfortunately neither of us know the virus name and I don't want to take the risk of plugging it to my Windows box again. Of course, in all probability the virus affects only Windows. (But I'm not sure) I want to know if I can safely plug the USB into my Ubuntu Lucid laptop and copy the stuff I need from the drive. If there are some precautions I need to follow what would they be?

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• Input/output (read) errors in Bacula while setting up a Tape Drive + Autochanger

  - by Kyle Brandt

  When running the label barcode command in bacula I am getting Input/output errors. I am just getting started in trying to set this up: Connecting to Storage daemon TapeDevice at ny-back01.ny.stackoverflow.com:9103 ... Sending label command for Volume "ACJ332" Slot 1 ... 3307 Issuing autochanger "unload slot 8, drive 0" command. 3304 Issuing autochanger "load slot 1, drive 0" command. 3305 Autochanger "load slot 1, drive 0", status is OK. block.c:1010 Read error on fd=5 at file:blk 0:0 on device "ULTRIUM-HH4" (/dev/st0). ERR=Input/output error. 3000 OK label. VolBytes=64512 DVD=0 Volume="ACJ332" Device="ULTRIUM-HH4" (/dev/st0) Catalog record for Volume "ACJ332", Slot 1 successfully created. Sending label command for Volume "ACJ331" Slot 2 ... 3307 Issuing autochanger "unload slot 1, drive 0" command. 3304 Issuing autochanger "load slot 2, drive 0" command. 3305 Autochanger "load slot 2, drive 0", status is OK. block.c:1010 Read error on fd=5 at file:blk 0:0 on device "ULTRIUM-HH4" (/dev/st0). ERR=Input/output error. 3000 OK label. VolBytes=64512 DVD=0 Volume="ACJ331" Device="ULTRIUM-HH4" (/dev/st0) Catalog record for Volume "ACJ331", Slot 2 successfully created. Sending label command for Volume "ACJ328" Slot 3 ... 3307 Issuing autochanger "unload slot 2, drive 0" command. 3304 Issuing autochanger "load slot 3, drive 0" command. 3305 Autochanger "load slot 3, drive 0", status is OK. block.c:1010 Read error on fd=5 at file:blk 0:0 on device "ULTRIUM-HH4" (/dev/st0). ERR=Input/output error. 3000 OK label. VolBytes=64512 DVD=0 Volume="ACJ328" Device="ULTRIUM-HH4" (/dev/st0) Catalog record for Volume "ACJ328", Slot 3 successfully created. Sending label command for Volume "ACJ329" Slot 4 ... 3307 Issuing autochanger "unload slot 3, drive 0" command. 3304 Issuing autochanger "load slot 4, drive 0" command. 3305 Autochanger "load slot 4, drive 0", status is OK. block.c:1010 Read error on fd=5 at file:blk 0:0 on device "ULTRIUM-HH4" (/dev/st0). ERR=Input/output error. 3000 OK label. VolBytes=64512 DVD=0 Volume="ACJ329" Device="ULTRIUM-HH4" (/dev/st0) Catalog record for Volume "ACJ329", Slot 4 successfully created. Sending label command for Volume "ACJ335" Slot 5 ... 3307 Issuing autochanger "unload slot 4, drive 0" command. 3304 Issuing autochanger "load slot 5, drive 0" command. 3305 Autochanger "load slot 5, drive 0", status is OK. block.c:1010 Read error on fd=5 at file:blk 0:0 on device "ULTRIUM-HH4" (/dev/st0). ERR=Input/output error. 3000 OK label. VolBytes=64512 DVD=0 Volume="ACJ335" Device="ULTRIUM-HH4" (/dev/st0) Catalog record for Volume "ACJ335", Slot 5 successfully created. Sending label command for Volume "ACJ334" Slot 6 ... 3307 Issuing autochanger "unload slot 5, drive 0" command. 3304 Issuing autochanger "load slot 6, drive 0" command. 3305 Autochanger "load slot 6, drive 0", status is OK. block.c:1010 Read error on fd=5 at file:blk 0:0 on device "ULTRIUM-HH4" (/dev/st0). ERR=Input/output error. 3000 OK label. VolBytes=64512 DVD=0 Volume="ACJ334" Device="ULTRIUM-HH4" (/dev/st0) Catalog record for Volume "ACJ334", Slot 6 successfully created. Sending label command for Volume "ACJ333" Slot 7 ... 3307 Issuing autochanger "unload slot 6, drive 0" command. 3304 Issuing autochanger "load slot 7, drive 0" command. 3305 Autochanger "load slot 7, drive 0", status is OK. block.c:1010 Read error on fd=5 at file:blk 0:0 on device "ULTRIUM-HH4" (/dev/st0). ERR=Input/output error. 3000 OK label. VolBytes=64512 DVD=0 Volume="ACJ333" Device="ULTRIUM-HH4" (/dev/st0) Catalog record for Volume "ACJ333", Slot 7 successfully created. Sending label command for Volume "ACJ330" Slot 8 ... 3307 Issuing autochanger "unload slot 7, drive 0" command. Bacula-dir: # Definition of file storage device Storage { Name = TapeDevice # Do not use "localhost" here Address = ny-back01.... # N.B. Use a fully qualified name here SDPort = 9103 Password = "..." Device = ULTRIUM-HH4 Media Type = LTO-4 Media Type = File Autochanger = Yes } Bacula-sd: Autochanger { Name = StorageLoader1U Device = ULTRIUM-HH4 Changer Command = "/etc/bacula/scripts/mtx-changer %c %o %S %a %d" Changer Device = /dev/sg5 } Device { Name = ULTRIUM-HH4 Media Type = LTO-4 Archive Device = /dev/st0 AutomaticMount = yes; AlwaysOpen = yes; RemovableMedia = yes; RandomAccess = no; AutoChanger = yes; RandomAccess = no; } Anyone knows what this means / why I am getting this?

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• Exchange Server 2003 Drive Error

  - by Saif Khan

  My exchange box went offline this AM. The logs show The device, \Device\Harddisk1, has a bad block. I tried running chkdsk D: /x /r but that didn't help either. I went to the Exchange Manager and tried to move the .stm file from D: to C: but got Exchange System Manager The database files in this store are corrupted. ID no: c104173b Exchange System Manager What else is there to try just to get this online for a few hours until I can get onsite to change the drive. This is a Windows Server 2003 server.

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• Why dd is not a reliable command to write bootable .iso files to USB thumb drive?

  - by Samik

  As the answers here indicate Ubuntu .iso s are not expected to boot if copied with dd to a USB thumb drive. Now my question is why is so that some Linux distributions have the option to directly write their bootable .iso file to a thumb drive with dd but some (read Ubuntu) have not(for Ubuntu I think it has to be converted to .img first). Is it for some architectural difference in .isos? Or is it due to any limitation of dd itself?I don't know if it is off-topic here. I can move it to a more proper place if the community thinks so or suggests one. Some explanation would be appreciable.

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• Weird Ubuntu Desktop Boot Partition On External Hard Drive

  - by Magnitus

  I have a Thinkpad with Windows 7. Last time I installed an Ubuntu/Windows dual boot, Windows was never same after and regularly got corrupted so this time, I installed Ubuntu on a separate external hard drive. I took a 500 GB external hard drive and used Windows to shrink the partition on it to 400 GB, freeing 100 GB to install Ubuntu. Then I modified the booting priority of my computer to boot from the external hard drive if present. Then, I installed Ubuntu desktop on the external hard drive using a DVD, picked the most simplistic partitioning scheme I could get away with (didn't go auto as it didn't include the external hard drive as a choice) and voilà. Fast forward some time and I'm trying to refresh my understanding of Linux partitions to install a bunch of servers, so I'm looking at the current partitioning scheme on my external hard drive and find the boot partition puzzling... sda is my integrated hard drive with Windows 7. sdb is my Ubuntu desktop external hard drive. Running parted on sdb, I get this: (parted) print Model: WD My Passport 0740 (scsi) Disk /dev/sdb: 500GB Sector size (logical/physical): 512B/512B Partition Table: msdos Number Start End Size Type File system Flags 1 1049kB 393GB 393GB primary ntfs boot 2 393GB 500GB 107GB extended 5 393GB 425GB 32.8GB logical linux-swap(v1) 6 425GB 500GB 74.6GB logical ext4 At this point, I'm wondering why the ntfs partition is flagged as "boot" and not my ext4 partition which is the partition that contains / (and by extension, /boot since it's not on its own separate partition). Looking at mtab only confirms what I already know: eric@eric-ThinkPad-W530:~$ sudo cat /etc/mtab /dev/sdb6 / ext4 rw,errors=remount-ro 0 0 proc /proc proc rw,noexec,nosuid,nodev 0 0 sysfs /sys sysfs rw,noexec,nosuid,nodev 0 0 none /sys/fs/cgroup tmpfs rw 0 0 none /sys/fs/fuse/connections fusectl rw 0 0 none /sys/kernel/debug debugfs rw 0 0 none /sys/kernel/security securityfs rw 0 0 udev /dev devtmpfs rw,mode=0755 0 0 devpts /dev/pts devpts rw,noexec,nosuid,gid=5,mode=0620 0 0 tmpfs /run tmpfs rw,noexec,nosuid,size=10%,mode=0755 0 0 none /run/lock tmpfs rw,noexec,nosuid,nodev,size=5242880 0 0 none /run/shm tmpfs rw,nosuid,nodev 0 0 none /run/user tmpfs rw,noexec,nosuid,nodev,size=104857600,mode=0755 0 0 none /sys/fs/pstore pstore rw 0 0 systemd /sys/fs/cgroup/systemd cgroup rw,noexec,nosuid,nodev,none,name=systemd 0 0 gvfsd-fuse /run/user/1000/gvfs fuse.gvfsd-fuse rw,nosuid,nodev,user=eric 0 0 /dev/sdb1 /media/eric/My\040Passport fuseblk rw,nosuid,nodev,allow_other,default_permissions,blksize=4096 0 0 My lack of understanding concerning this is not vital to anything (this is only my development desktop partition), but somehow annoys me. Any insight that could shed some light on this would be welcome.

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• how to use gparted to partion 2 drives as 1

  - by user281745

  I have my lenovo t43 and I have a SATA extra HD drive instead of the CD drive and I have in it a 250 GB hard drive and in my HD caddy I have a 40 GB hard drive I would like to use gparted to partition these 2 drives as 1 i would like to have the 250 GB as a extended part of the 40 GB cause i already have Ubuntu Installed on it, they are right now not side by side im not sure how to do this so please list by step by step thank you http://imgur.com/dE0B7dy,qRRPgoB http://imgur.com/dE0B7dy,qRRPgoB#1

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• Data transfer is extrem slow after partitioning extern usb drive

  - by user125912

  I bought an extern usb 3.0 drive with 500 gb capacity. OS is Windows 7. I use it with an usb 2.0 slot, no prob. Initially I used it without making several partitions and it was fast as hell. Then I had the great idea to make partitions, one for programs, one for data and one for backup. I chose the free EASEUS Partition Master 9.1.1. and ended up with these partitions: F:Apps, primary, NTFS, 100gb H:Data, logic, NTFS, 250gb B:Backup, logic, NTFS, 150gb THE PROBLEM: When I copy files from C: to F: I get a transfer rate of about 100 KB/S ! When I copy files from C: to H: I get a transfer rate of about 4 MB/S ! thats all muuuch to slow, slower then before. What can I do to speed the shit up? Thanks in advance!

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• Analyse frequencies of date ranges in Google Drive

  - by wnstnsmth

  I have a Google Drive spreadsheet where I would like to compute occurrences of date ranges. As you can see in my sheet, there is a column date_utc+1 which contains almost random date data. https://docs.google.com/spreadsheet/ccc?key=0AhqMXeYxWMD_dGRkVGRqbkR3c05mWUdhYkJWcFo2Mmc What I would like to do is 1) put the date values into bins of 6 hours each, i.e. 12/5/2012 23:57:04 until 12/6/2012 0:03:17 would be in the first bin, 12/6/2012 11:20:53 until 12/6/2012 17:17:07 in the second bin, and so forth. Then, I would like to count the occurrence of those bins, such as bin_from bin_to freq ----------------------------------------------- 12/5/2012 23:57:04 12/6/2012 0:03:17 2 12/6/2012 11:20:53 12/6/2012 17:17:07 19 ... ... ... Hope it is clear what I mean. Partial hints are very welcome as well since I am pretty new to spreadsheeting.

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