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Thread: Sata Raid

  1. #1
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    Question Sata Raid

    I searched the forums but couldn't find much information regarding SATA Raid from actual users. Those who use it, is there much of a performance degredation on your server?

    I currently use Cpanel backing up to a secondary IDE drive, which bogs down the server every night. So I am looking for better alternatives. Plus raid offers the ability to just swap out the bad drive in minutes. Rather than doing a fresh install and restoring all accounts, which can cause hours of downtime.

    Also, with raid, would it be good to also include a 3rd drive to put cpanel backups on, just in case the system was compromised?
    Mark

  2. #2
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    RAID1 should perform better (for reading), as the data can come from either disc, so which ever drive head is closest to the data will return first, this can decrease the access time.

    Writing performance should be the same as for a single disc.

    However, the big caveat here is that this depends on the controller quality.

    I personally would have a 3rd drive in there to write a backup dump to which you can then copy offsite. If you have offsite backups made using rsync then this option is not necessary, though a 3rd disc in the server means you have a spare always on hand for replacing one of the raid drives if one fails.

  3. #3
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    SATA RAID1 will yield slightly better performance but it is important to remember RAID is not a backup. RAID1 simply mirrors the contents of drive0 to drive1 "in realtime". If something gets deleted or messed up on drive0 it will be the same on drive1. RAID1 increases the reliabilty of the system (server can survive a single drive failure) but you will still want to have backups of the server.
    "Arms discourage and keep the invader and plunderer in awe, and preserve order in the world as well as property... Horrid mischief would ensue were the law-abiding deprived of the use of them." - Thomas Paine

  4. #4
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    I have found that most hardware raid controllers embedded in MBs aren't actually hardware, but bios based software. This makes setting up a hardware raid with linux a bit tricky. You will probably want to go with software raid, due to it's ease of use (no recompile) and relative performance.
    Peter Hall
    Tera Web Hosting
    UK Web Hosting and Backup Storage

  5. #5
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    I was going to post about how HW raid is superior to SW but.... google says otherwise (and who am I to argue!)

    Here's some benchmarks:
    http://www.chemistry.wustl.edu/~gelb/castle_raid.html

    Here's an excellent link:
    http://www.tldp.org/HOWTO/Software-RAID-HOWTO.html

    I was surprised!

  6. #6
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    gbjbaanb,

    your links are all based on Raid 5/10/50, not Raid 1, which I think XION is thinking of. Raid 5 is of course better (also more expensive), and REQUIRES at least 3 disks. I am not sure XION will go for that.

    XION, you should expect a slightly slower write speed with Raid1, SATA itself shoud not change the speed (though it may be faster than your IDE disk).

    For info check this like: http://linuxmafia.com/faq/Hardware/sata.html, there are good links in there.

    And yes, software Raid can be faster with linux, most Raid cards don't do real ata raid with Linux. So they are a kind of slower software raid that you have to pay for. 0f course, real HW raid is faster.

  7. #7
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    Originally posted by gbjbaanb
    I was surprised!
    Software RAID can under certain circumstances be faster than a true hardware solution, but in real life the answer is hardware wins. In the test you linked to they tested a 3WARE card (a budget raid controller) against a Xeon processor (the server was only running their i/o tests) so yes it did best the processor on the RAID card. However if the server were loaded up with sites and being used so that the Xeon had other work to do I bet you even that budget RAID controller would have done much, much better.
    Much more important though is SW RAID depends on the OS and the RAID drivers in order to work. If the OS gets hosed, trying to access the drive again becomes a nightmare.
    "Arms discourage and keep the invader and plunderer in awe, and preserve order in the world as well as property... Horrid mischief would ensue were the law-abiding deprived of the use of them." - Thomas Paine

  8. #8
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    Wow, thanks for all the great info guys Looks like raid will definatly be an option for my next server
    Mark

  9. #9
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    In my research, I found a link: http://www.tweakers.net/reviews/557

    This is stunning, SATA RAID hardware controllers (and yes, the Areca controller costs more than my PC) but look at the RAID5 performance with more than 3 discs. (eg http://www.tweakers.net/reviews/557/25)

    (oh, and if you want just to read about this, try slashdot as there is some nice info in the noise http://ask.slashdot.org/article.pl?s...&tid=185&tid=4)

  10. #10
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    Originally posted by gbjbaanb
    In my research, I found a link: http://www.tweakers.net/reviews/557

    nice link!

  11. #11
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    With the proper controller(s) you'll find that performance continues to increase as you add more drives. This goes back to the main frame days, where they always said the way to improve disk i/o was to throw more spindles at the system.
    Not too long ago when I was at HP for some classes we got to play around with the smart array 6404 controller as well as the storageworks xp1024. In benchmarking the 6404 controller performance kept improving all the way up to the 56 drive max it supported. The xp1024 behaved the same way as they checked performance in various configurations (maxes out at 1024 drives)
    "Arms discourage and keep the invader and plunderer in awe, and preserve order in the world as well as property... Horrid mischief would ensue were the law-abiding deprived of the use of them." - Thomas Paine

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