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Asked: 2010-03-04 18:20:04 +0800 CST

RAID array Considerations - Any advice?

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We just bought a Dell PowerEdge r510 (12 drive bays) that will fill the role of an archive server. We have 6 drives (1TB each) installed.

The plan is to have all the drives in a single RAID array and carve out an OS partition and an Archive partition.

We intend to expand to all 12 drives, but need to preserve the main archive partition when we do (i.e. we'd like to add more drives and expand the space available on the archive partition, not create another array or another partition to allocate the additional space).

Questions:

  • Is there a good way to do this (if at all)?
  • What would the preferred RAID type be if it's possible (5, 1+0, etc.)?
raid hardware-raid

3 Answers

  1. Best Answer

    If I could suggest a slight modification of your plans:

    1. Put the OS on two smaller disks and mirror them.
    2. Create a second array, preferably RAID 6 with a hot spare, and make it a dynamic partition within Windows so you can expand later.

    Don't dynamically expand volumes that are on the system disk. I've heard bad things about that. Keep the system separate from the data for performance reasons but also for volume corruption reasons.

    RAID 6 is to counter the higher possibility of encountering a URE while rebuilding a failed RAID set. (Some good reading on the topic here, here and here over at the Storage Mojo blog). Even with RAID controllers that scrub drives looking for problems, I recommend an array that can sustain at least two drive failures before data loss. Thus my recommendation for RAID 6. The hot spare makes sure the rebuild happens as quickly as possible even if it's 3AM and you turned your cell phone's text message alert off in your sleep (if you haven't done that yet, you will someday =) ).

    In addition, I'm sure you know that RAID is not a backup so it would be good to archive the data to tape once in a while and put it in a bank vault.

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  2. There was some good discussion yesterday about RAID5 vs. 6

    All of Wesley's suggestions are spot on, you're better off w/ the "data array" completely separate from the system array, and for an archive, the possible performance hit of RAID6 shouldn't be an issue.

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  3. WRT to RAID 5/6 v 10, I would go with 10 for speed and sanity. A degraded RAID 10 is faster and easier to rebuild than a degraded RAID 5/6. To me it's worth the loss in storage space.

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