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On 1 Feb 2010, at 11:58, J. Roeleveld wrote: |
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> ... |
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> I am currently installing a new server and am using Linux software |
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> raid to |
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> merge 6 * 1.5TB drives in a RAID5 configuration. |
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> |
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> Creating the RAID5 takes over 20 hours (according to " cat /proc/ |
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> mdstat ") |
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> |
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> Is there a way that will speed this up? The drives are new, but |
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> contain random |
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> data left over from some speed and reliability tests I did. I don't |
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> care about |
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> keeping the current 'data', as long as when the array is reliable |
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> later. |
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> |
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> Can I use the " --assume-clean " option with mdadm and then expect |
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> it to keep |
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> working, even through reboots? |
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> Or is this a really bad idea? |
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It wasn't my intention to chide you - I don't use software RAID |
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myself, and your question piqued my curiosity - but the first three |
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Google hits for "assume-clean" indicate that this isn't safe to use |
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with RAID5. |
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The 4th Google hit contains an extract from the manpage: |
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... It can |
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also be used when creating a RAID1 or RAID10 if you want |
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to avoid the initial resync, however this practice -- |
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while normally safe -- is not recommended. Use this |
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only if you really know what you are doing. |
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I have to say that I don't fully understand this. I would have thought |
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that one could pretend the entire array was empty, and the RAID driver |
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would just overwrite the disk as you write to the filesystem. The |
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parts used by the filesystem are the only parts you care about, and I |
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wouldn't have thought it would matter if the unused parts weren't in |
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sync. I would be delighted if someone could explain me. |
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I kinda expected this 20 hours to be spent verifying that the disks |
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contain no bad sectors, which would really hose you if it were the case. |
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But OTOH, 20 hours does not seem an outrageous amount of time for |
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building a 7.5TB array. You're not going to do this often, and you |
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want it done right. |
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It would be interesting to know whether hardware RAID would behave any |
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differently or allow the sync to perform in the background. I have |
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only 1.5TB in RAID5 across 4 x 500gb drives at present; IIRC the |
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expansion from 3 x drives took some hours, but I can't recall the |
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initial setup. |
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Stroller. |
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