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  • Bad performance with Linux software RAID5 and LUKS encryption

    - by Philipp Wendler
    I have set up a Linux software RAID5 on three hard drives and want to encrypt it with cryptsetup/LUKS. My tests showed that the encryption leads to a massive performance decrease that I cannot explain. The RAID5 is able to write 187 MB/s [1] without encryption. With encryption on top of it, write speed is down to about 40 MB/s. The RAID has a chunk size of 512K and a write intent bitmap. I used -c aes-xts-plain -s 512 --align-payload=2048 as the parameters for cryptsetup luksFormat, so the payload should be aligned to 2048 blocks of 512 bytes (i.e., 1MB). cryptsetup luksDump shows a payload offset of 4096. So I think the alignment is correct and fits to the RAID chunk size. The CPU is not the bottleneck, as it has hardware support for AES (aesni_intel). If I write on another drive (an SSD with LVM) that is also encrypted, I do have a write speed of 150 MB/s. top shows that the CPU usage is indeed very low, only the RAID5 xor takes 14%. I also tried putting a filesystem (ext4) directly on the unencrypted RAID so see if the layering is problem. The filesystem decreases the performance a little bit as expected, but by far not that much (write speed varying, but 100 MB/s). Summary: Disks + RAID5: good Disks + RAID5 + ext4: good Disks + RAID5 + encryption: bad SSD + encryption + LVM + ext4: good The read performance is not affected by the encryption, it is 207 MB/s without and 205 MB/s with encryption (also showing that CPU power is not the problem). What can I do to improve the write performance of the encrypted RAID? [1] All speed measurements were done with several runs of dd if=/dev/zero of=DEV bs=100M count=100 (i.e., writing 10G in blocks of 100M). Edit: If this helps: I'm using Ubuntu 11.04 64bit with Linux 2.6.38. Edit2: The performance stays approximately the same if I pass a block size of 4KB, 1MB or 10MB to dd.

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  • Reusing slot numbers in Linux software RAID arrays

    - by thkala
    When a hard disk drive in one of my Linux machines failed, I took the opportunity to migrate from RAID5 to a 6-disk software RAID6 array. At the time of the migration I did not have all 6 drives - more specifically the fourth and fifth (slots 3 and 4) drives were already in use in the originating array, so I created the RAID6 array with a couple of missing devices. I now need to add those drives in those empty slots. Using mdadm --add does result in a proper RAID6 configuration, with one glitch - the new drives are placed in new slots, which results in this /proc/mdstat snippet: ... md0 : active raid6 sde1[7] sdd1[6] sda1[0] sdf1[5] sdc1[2] sdb1[1] 25185536 blocks super 1.0 level 6, 64k chunk, algorithm 2 [6/6] [UUUUUU] ... mdadm -E verifies that the actual slot numbers in the device superblocks are correct, yet the numbers shown in /proc/mdstat are still weird. I would like to fix this glitch, both to satisfy my inner perfectionist and to avoid any potential sources of future confusion in a crisis. Is there a way to specify which slot a new device should occupy in a RAID array? UPDATE: I have verified that the slot number persists in the component device superblock. For the version 1.0 superblocks that I am using that would be the dev_number field as defined in include/linux/raid/md_p.h of the Linux kernel source. I am now considering direct modification of said field to change the slot number - I don't suppose there is some standard way to manipulate the RAID superblock?

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  • Software RAID 1 Configuration

    - by Corve
    I have created a software RAID 1 quite some while ago and it always seemed to work for me. However I am not completely sure that I have configured everything right and do not have the experience to check so I would be very grateful for some advice or just verification that all seems right so far. I am using Linux Fedora 20 (32 bit with plans to upgrade to 64bit) The RAID 1 should consist of two 1TB SATA hard drives. This is the output of mdadm --detail /dev/md0 /dev/md0: Version : 1.2 Creation Time : Sun Jan 29 11:25:18 2012 Raid Level : raid1 Array Size : 976761424 (931.51 GiB 1000.20 GB) Used Dev Size : 976761424 (931.51 GiB 1000.20 GB) Raid Devices : 2 Total Devices : 1 Persistence : Superblock is persistent Update Time : Sat Jun 7 10:38:09 2014 State : clean, degraded Active Devices : 1 Working Devices : 1 Failed Devices : 0 Spare Devices : 0 Name : argo:0 (local to host argo) UUID : 1596d0a1:5806e590:c56d0b27:765e3220 Events : 996387 Number Major Minor RaidDevice State 0 0 0 0 removed 1 8 0 1 active sync /dev/sda The RAID is mounted successfully: friedrich@argo:~ ? sudo mount -l | grep md0 /dev/md0 on /mnt/raid type ext4 (rw,relatime,data=ordered) Basically my question are: Why do I only have 1 active device? What does the State removed at bottom mean? Also I noticed some strange error messages that I see on the console on system start and shutdown and always repeating in the background when I switch with Ctrl + Alt + F2: ... ata2: irq_stat 0x00000040 connection status changed ata2: SError: { CommWake DevExch } ata2: COMRESET failed (errno=-32) ata2: exception Emask 0x10 SAct 0x0 SErr 0x4040000 action 0xe frozen ata2: irq_stat 0x00000040 connection status changed ata2: SError: { CommWake DevExch } ata2: exception Emask 0x10 SAct 0x0 SErr 0x4040000 action 0xe frozen ... Are these errors related to the RAID? Something seems wrong with the SATA devices.. All together the system works (I can read and write to the mounted raid) but I always had these strange errors on startup shutdown (probably always in the background). Thx for your help

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  • Introduction to Lean Software Development and Kanban Systems – Build Integrity and Quality In

    - by Ben Griswold
    In this post, we’ll continue the series by concentrating on Principle #3: Build Integrity and Quality In.   In the next part of the series, we’ll dive into Principle #4: Defer Commitment and Decide As Late As Possible. And I am going to be a little obnoxious about listing my Lean and Kanban references with every series post.  The references are great and they deserve this sort of attention.  

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  • Graphical quality of open source vs. commercial games

    - by Toktik
    I'm new in Game development. I have researched many open source games. But I have not met any open source game which has high quality graphics, comparable to these found in commercial games. What is the reason for this? Are open source game engines not advanced enough to support such graphics or is there just a lack of assets, textures and models? I know that this question is very general, I would like to hear some points of view.

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  • Do software developers know what engineers actually do?

    - by lorin
    Software development is often contrasted with the traditional branches of engineering, most commonly civil or mechanical engineering. For example: "Software development isn't like engineering, it's like craftsmanship!" "Software development isn't like engineering, but it should be!" Do software developers understand what it is that engineers do and how they do it? At least, do they understand it well enough to be able to make an informed comparison with what software developers do?

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  • Data Quality Services Performance Best Practices Guide

    This guide details high-level performance numbers expected and a set of best practices on getting optimal performance when using Data Quality Services (DQS) in SQL Server 2012 with Cumulative Update 1. Schedule Azure backupsRed Gate’s Cloud Services makes it simple to create and schedule backups of your SQL Azure databases to Azure blob storage or Amazon S3. Try it for free today.

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  • How to Tell a Hardware Problem From a Software Problem

    - by Chris Hoffman
    Your computer seems to be malfunctioning — it’s slow, programs are crashing or Windows may be blue-screening. Is your computer’s hardware failing, or does it have a software problem that you can fix on your own? This can actually be a bit tricky to figure out. Hardware problems and software problems can lead to the same symptoms — for example, frequent blue screens of death may be caused by either software or hardware problems. Computer is Slow We’ve all heard the stories — someone’s computer slows down over time because they install too much software that runs at startup or it becomes infected with malware. The person concludes that their computer is slowing down because it’s old, so they replace it. But they’re wrong. If a computer is slowing down, it has a software problem that can be fixed. Hardware problems shouldn’t cause your computer to slow down. There are some rare exceptions to this — perhaps your CPU is overheating and it’s downclocking itself, running slower to stay cooler — but most slowness is caused by software issues. Blue Screens Modern versions of Windows are much more stable than older versions of Windows. When used with reliable hardware with well-programmed drivers, a typical Windows computer shouldn’t blue-screen at all. If you are encountering frequent blue screens of death, there’s a good chance your computer’s hardware is failing. Blue screens could also be caused by badly programmed hardware drivers, however. If you just installed or upgraded hardware drivers and blue screens start, try uninstalling the drivers or using system restore — there may be something wrong with the drivers. If you haven’t done anything with your drivers recently and blue screens start, there’s a very good chance you have a hardware problem. Computer Won’t Boot If your computer won’t boot, you could have either a software problem or a hardware problem. Is Windows attempting to boot and failing part-way through the boot process, or does the computer no longer recognize its hard drive or not power on at all? Consult our guide to troubleshooting boot problems for more information. When Hardware Starts to Fail… Here are some common components that can fail and the problems their failures may cause: Hard Drive: If your hard drive starts failing, files on your hard drive may become corrupted. You may see long delays when you attempt to access files or save to the hard drive. Windows may stop booting entirely. CPU: A failing CPU may result in your computer not booting at all. If the CPU is overheating, your computer may blue-screen when it’s under load — for example, when you’re playing a demanding game or encoding video. RAM: Applications write data to your RAM and use it for short-term storage. If your RAM starts failing, an application may write data to part of the RAM, then later read it back and get an incorrect value. This can result in application crashes, blue screens, and file corruption. Graphics Card: Graphics card problems may result in graphical errors while rendering 3D content or even just while displaying your desktop. If the graphics card is overheating, it may crash your graphics driver or cause your computer to freeze while under load — for example, when playing demanding 3D games. Fans: If any of the fans fail in your computer, components may overheat and you may see the above CPU or graphics card problems. Your computer may also shut itself down abruptly so it doesn’t overheat any further and damage itself. Motherboard: Motherboard problems can be extremely tough to diagnose. You may see occasional blue screens or similar problems. Power Supply: A malfunctioning power supply is also tough to diagnose — it may deliver too much power to a component, damaging it and causing it to malfunction. If the power supply dies completely, your computer won’t power on and nothing will happen when you press the power button. Other common problems — for example, a computer slowing down — are likely to be software problems. It’s also possible that software problems can cause many of the above symptoms — malware that hooks deep into the Windows kernel can cause your computer to blue-screen, for example. The Only Way to Know For Sure We’ve tried to give you some idea of the difference between common software problems and hardware problems with the above examples. But it’s often tough to know for sure, and troubleshooting is usually a trial-and-error process. This is especially true if you have an intermittent problem, such as your computer blue-screening a few times a week. You can try scanning your computer for malware and running System Restore to restore your computer’s system software back to its previous working state, but these aren’t  guaranteed ways to fix software problems. The best way to determine whether the problem you have is a software or hardware one is to bite the bullet and restore your computer’s software back to its default state. That means reinstalling Windows or using the Refresh or reset feature on Windows 8. See whether the problem still persists after you restore its operating system to its default state. If you still see the same problem – for example, if your computer is blue-screening and continues to blue-screen after reinstalling Windows — you know you have a hardware problem and need to have your computer fixed or replaced. If the computer crashes or freezes while reinstalling Windows, you definitely have a hardware problem. Even this isn’t a completely perfect method — for example, you may reinstall Windows and install the same hardware drivers afterwards. If the hardware drivers are badly programmed, the blue-screens may continue. Blue screens of death aren’t as common on Windows these days — if you’re encountering them frequently, you likely have a hardware problem. Most blue screens you encounter will likely be caused by hardware issues. On the other hand, other common complaints like “my computer has slowed down” are easily fixable software problems. When in doubt, back up your files and reinstall Windows. Image Credit: Anders Sandberg on Flickr, comedy_nose on Flickr     

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  • Free Webcast: Oracle's Data Quality Solutions for Oracle Siebel CRM

    - by andrea.mulder
    Do you want to maximize cross-sell and upsell opportunities? Boost call center productivity? Reduce marketing costs? Improve customer retention? I believe the appropriate answers are "yes", "Yes", "YES", and "YES!!!" Attend this free webcast Oracle's Data Quality Solutions for Siebel CRM on Thursday, March 3rd at 11am PT and learn how to get more value out of your current Siebel CRM investment. Register today!

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  • Optimize video filesize without quality loss

    - by user12015
    Is there a simple way (on the command line - I want to write a script which compresses all videos in a folder) to reduce the filesize of a video (almost) without quality loss? Is there a method which works equally well for different video format (mp4, flv, m4v, mpg, mov, avi)? I should mention that most of the videos I would like to compress are downloaded web-videos (mp4, flv), so it's not clear if there is much room for further compression.

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  • PASS Data Architecture VC presents Neil Hambly on Improve Data Quality & Integrity using Constraints

    On Tuesday June 19th 12PM noon Central, Neil Hambly will discuss "Leveraging the power of constraints to improve both data quality and performance of your databases." What are your servers really trying to tell you? Find out with new SQL Monitor 3.0, an easy-to-use tool built for no-nonsense database professionals.For effortless insights into SQL Server, download a free trial today.

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  • SQL Down Under Podcast - Gadi Peleg - Data Quality Services

    - by Greg Low
    Well it's been a few months but I'm back on a roll creating some SQL Down Under podcasts. The first out the door is an interview with Gadi Peleg from the SQL Server team, introducing Data Quality Services.Gadi came to Microsoft when Zoomix was acquired.Details of this podcast (and other available podcasts) are here: http://www.sqldownunder.com/Resources/Podcast.aspxHope you enjoy it even though there are some telling signs that I recorded it at 3AM :-)If you are using iTunes, you can also subscribe here: http://itunes.apple.com/au/podcast/sql-down-under/id503822116?mt=2

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  • Quality Reseller Hosting Services Provider

    Finding a quality reseller hosting service provider is not at all difficult. All an enterprise needs to know is the very essence of reseller web hosting and its concept apart from knowing certain oth... [Author: John Anthony - Computers and Internet - June 04, 2010]

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  • Quality SEO Services For Hire

    With the many websites being continuously uploaded to the internet with each passing minute of the day, one may wonder how he or she can get their web site noticed with the ever increasing competition. Many people are beginning to turn to quality SEO services for help with their web site optimization needs.

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  • The Doorway to a Quality SEO Company

    To figure out what we saw in the short breather, let us try to make a synopsis from a bird's eye point of view. An SEO service comprises of some simple yet mandatory basics which should not be refuted for the quality maintenance. From the professional aspect, it is a rare combination of database management, application of programming logic, statistical analysis and innovative marketing.

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  • Quality SEO Services to Guarantee Your Online Popularity

    Internet Marketing strategies aim to give you the edge you need to succeed in the online scenario. Whether its business, outsourcing, or for popularity purposes, Internet Marketing aims to put you on top and keep your competitions down. Keep in mind that implementation of its strategies alone is not enough to guarantee that you're going to meet your goals. In most cases, you have to opt for expert implementation of quality SEO Services to ensure your success in the online setting.

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  • Quality Backlinks Are Essential For Search Engine Optimization!

    Quality backlinks are essential for search engine optimization. Backlinks are links that start on another website and they point to your page, which means that you have very low control on them. Many web developers prefer to go into negotiations when it comes to backlink building, discussing various matters and aspects with the web masters of the other sites.

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  • Importance of Quality Link Building in SEO

    Link building is all about posting links to your website at relevant sites. The sites could be anything from third party sites to blogs and reviews. A quality link building company can take care of this for you and it is found to be the best way of increasing the inflow of traffic into your website.

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  • Create Quality Content For SEO

    Quality content relies on several variables in order to be effective for search engine optimization. First and foremost, a writer's articles and page content should be truly genuine and informative. Genuine content is that which has not been published previously on another site or blog.

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  • TestRail 1.3 Test Management Software released

    Gurock Software just announced version 1.3 of its test management software TestRail. TestRail is a web-based test case management software that helps software development teams and QA departments to efficiently manage, track and organize their software testing efforts.

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