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I'm very new to RAID servers, in fact I'm new to any kind of server management, so please forgive me if this question is badly phrased.

I'm considering buying a RAID5 server with four 4TB drives. I was told by the salesman that while the RAID server would allow for fault tolerance, every time I remove a disk I will have to format it before reinserting it into the server. Is this always the case? Are there models I can buy where this will not be required?

Thanks!

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I've used many various RAID controllers on Dells, HP and IBM servers and not once formatted a drive when adding it. Perhaps they mean "Pulling and replacing a drive will result in an array rebuild"? Could you clarify? –  jscott Oct 7 '13 at 10:51
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He probably doesn't mean reformat, but the RAID will require rebuilding as the moment you pull out a drive the RAID will be degraded and the drive out of date. Why is this a problem, and why do you need to pull disks on a regular basis? –  Dan Oct 7 '13 at 10:52
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Also, RAID5 with 4x 4TB disks is a recipe for disaster due to the length of time it will take to rebuild. You should consider an alternative RAID configuration. –  Dan Oct 7 '13 at 10:53
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RAID 5 with 4TB drives? Eesh. Personally I'd prefer a RAID10 here. Have a look at this question to get an overview of different RAID types and their pros/cons. –  tombull89 Oct 7 '13 at 10:53

2 Answers 2

Every time you remove a drive, and reinsert it later (or insert a new one), RAID will have to be rebuilt. The computer/controller will have to go through all data, and most probably write new data (parity, or data generated from other drivers+parity) to the new/reinserted drive. With 4TB drives, this takes alot of time.

I'd consider other options (maybe even RAID6), since rebuild causes alot of load on the drives, and there is a higher risk of failure of some other drive during rebuild, causing data loss (especially with drives with low normal use).

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RAID configuration is written on the drive. There is a label stating "I'm drive 4 of raid array X4HKB5" where the code is a kind of GUID. This allows you to move disks on the RAID adapter (if you do it, do it only while computer is turned off).

If you insert a disk that was previously part of another RAID5 array in your server it may recognize the label and tell you there's a new corrupted volume (because other drives of X4HKB5 are not found).

If the disk you're adding is not new, it's easier to destroy all partitions on it before insertion.

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