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Thread: RAID10 query?

  1. #1

    RAID10 query?

    Hello,

    I am still in the process of putting the business together and I was going to use r1soft CDP backups to a dedicated box with 4 x 1TB drives and RAID10.

    I have found that another web host is doing something similar but they have 24 1TB drives. With RAID10, I believe that each drive will have the same content as it is replicated or am I wrong?

    Will the other webhost only have 1TB of space or will they have 24TB?

    Confused here, so please help me out.

    Thanks

  2. #2
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    24x1TB HDDs in RAID 10 = 12TB space

    Technically it'll end up being around 10.8TB due to the ~10% loss in disk space due to partitioning, etc.
    Jacob Wall - GetCloak.com

  3. #3
    Quote Originally Posted by Jacob Wall View Post
    24x1TB HDDs in RAID 10 = 12TB space

    Technically it'll end up being around 10.8TB due to the ~10% loss in disk space due to partitioning, etc.
    Thanks for the quick reply. So am I right in thinking that the backups would be spread over 12 drives and each drive will have the same backups on?

  4. #4
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    Raid 10 is just a striped pair of mirrors. So, with 24 drives you will have 12 mirrored pair then a striped volume over the entire array. The end result is 1/2 of the total capacity.

    Typically, you would want to use raid 5 or 6 for a backup volume. They may be slow to write, but so is dragging data across the network and compressing it into an image. Especially with a large number of disks, you'll get much more out of a 24 disk raid 6.
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  5. #5
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    Quote Originally Posted by needtoknow View Post
    Thanks for the quick reply. So am I right in thinking that the backups would be spread over 12 drives and each drive will have the same backups on?
    The data would be spread across all 24 drives, though every other drive would carry the same information.

    It'll act just as RAID 10 does with 4 drives, but instead with 24 drives.

    If he's doing backups though, why not RAID 5? It'll give you a lot more disk space.

    4x1TB in RAID 5 = 3TB(~2.7TB after everything is said and done)
    24x1TB in RAID 5 = 18TB(~16.2TB after everything is said and done)
    Jacob Wall - GetCloak.com

  6. #6
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    Quote Originally Posted by needtoknow View Post
    Thanks for the quick reply. So am I right in thinking that the backups would be spread over 12 drives and each drive will have the same backups on?
    The way Raid10 works is that it's a striped set of mirrored drives.

    So you have 12 drives that have data, another set of 12 that have the SAME data. The data is striped (i.e. split up among the 12 drives) for read/write performance. If one drive fails it's mirror will take over. In this situation you could theoretically have up to 12 drives fail and not lose anything however you could also lose as little as 2 drives and lose data.

    So if you have these 24 drives:
    1. Drive A / Drive B
    2. Drive A / Drive B
    3. Drive A / Drive B
    4. Drive A / Drive B
    5. Drive A / Drive B
    6. Drive A / Drive B
    7. Drive A / Drive B
    8. Drive A / Drive B
    9. Drive A / Drive B
    10. Drive A / Drive B
    11. Drive A / Drive B
    12. Drive A / Drive B

    You could lose "A drives" 1~6" and "B drives" 7~12 and not have any data loss (or any mix-match from opposite sides but as soon as you have Drive A and B fail on the same line (i.e. Drive number 4 A and Drive number 4 B fail) you lose that portion of data. Depending on the file system (be it Raid10 or raid1) you could lose everything or only the data stored on those drives.

    Raid1 and raid10 would offer the same redundancy against drive failure while raid10 will offer greater performance and an increased risk of losing everything should two mirrored drives fail.
    Last edited by MikeDVB; 02-09-2011 at 02:41 PM.
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  7. #7
    Forgive my ignorance but if you have 4x1TB Drive with raid10 on your customer servers, can i allot up to 4TB of space or 1TB?

    Thanks

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    Quote Originally Posted by needtoknow View Post
    Forgive my ignorance but if you have 4x1TB Drive with raid10 on your customer servers, can i allot up to 4TB of space or 1TB?

    Thanks
    This should help you. http://www.ibeast.com/content/tools/...c/RaidCalc.asp

    To answer your question, you'd get 1.8TB after everything(OS, partitioning, etc) is done.
    Jacob Wall - GetCloak.com

  9. #9
    Awesome thanks Jacob, so now I know!

    I also found this interactive tutorial that explained it better:
    http://www.acnc.com/04_01_10.html

    I was underthe impression that all data was on say Drive A and copied to B, C and D incase A fails!

    Thanks again guys!

  10. #10
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    Quote Originally Posted by needtoknow View Post
    Awesome thanks Jacob, so now I know!

    I also found this interactive tutorial that explained it better:
    http://www.acnc.com/04_01_10.html

    I was underthe impression that all data was on say Drive A and copied to B, C and D incase A fails!

    Thanks again guys!
    No problem, I know it can be confusing at times when you're first learning about it.
    Jacob Wall - GetCloak.com

  11. #11
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    We run a 24x1tb raid-10 for a CDP server. We do this because in Raid 5 the performance was absolutely abysmal. This was with CDP v2 and not their v3 which supposedly has better performance. We did the math and with a raid-5 in our case we'd run out of i/o before ever coming close to using the disk space. We found we could fit more on a raid-10 system as we'd get the better i/o and get closer to using the total disk space available. Everyones situation will be different though so raid-5, 10 or no raid at all will depend on what you're backing up and how often.
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  12. #12
    24 hdds in raid5 not the best idea. In case when 2 drives dead you will not be able to restore your data. More drives you have, more chances to get 2 dead drives.
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  13. #13
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    Quote Originally Posted by alnitech View Post
    24 hdds in raid5 not the best idea. In case when 2 drives dead you will not be able to restore your data. More drives you have, more chances to get 2 dead drives.
    Raid10 could see the same issue if you're unlucky with 2 drives dead on opposite sides of the mirror. Raid6 would be a bit better compared to Raid5 but then again parity calculations would take longer and as such i/o would suffer.
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