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andrew_va

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andrew_va

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August 8th, 2005 22:00

Basic LUN / RAID 5 question

Hey Guys,
I have a Powervault 650F and 4 630's. I want to make it one gigantic RAID 5. I will not be backing it up in any way, it is purely an experiment.

I know there is a maximum of 16 drives assignable per LUN.

Is it possible to assign multiple LUNS to a single logical RAID 5 volume? Or is my total RAID 5 size limited to the sum of 16 drives?

I can't seem to find anything in the Data Administrator documentation that tells me HOW I create the virtual disks once I have my LUNS bound. If anyone can shed light on this or tell me what keywords to look up I would appreciate it.

Thanks,
Andrew
  • Dev Mgr

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    Posted August 9th, 2005 11:00

    The PV650F doesn't support metaluns like the CX-series from EMC does, and a LUN can only exist in a single set of disks (aka disk pool (AX100 terminology) or raid group (FC- and CX-terminology)). So you're indeed limited to 16 x max drive size (73GB with the last firmware Dell released for the unit).
  • andrew_va

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    Posted August 9th, 2005 13:00

    DevMgr,
    Thanks for the reply.

    So, let's say I have one 650F and four 630's.

    Each hold 10 drives, for a total of 50 drives.

    Since I can have a max of 16 drives per LUN, if I maxed out each LUN I would have:

    LUN 0 (16 drives) - 1 logical volume in Windows (I'll call it drive G)
    LUN 1 (16 drives) - 1 logical volume in Windows (I'll call it drive H)
    LUN 2 (16 drives) - 1 logical volume in Windows (I'll call it drive I)
    2 Global hot spares
    -------------------
    Total = 50 drives

    Would this be right? (no way to assemble G: H: & and I: into one volume?)

    In reality, my setup will probably be more like this:

    LUN 0 (10 drives) in DAE1 - 1 logical volume in Windows (I'll call it drive G)
    LUN 1 (10 drives) in DAE2 - 1 logical volume in Windows (I'll call it drive H)
    LUN 2 (10 drives) in DAE3 - 1 logical volume in Windows (I'll call it drive I)
    LUN 3 (10 drives) in DAE4 - 1 logical volume in Windows (I'll call it drive J)
    10 Global Hot Spares in DAE 5

    Thanks for your input,

    Andrew

    Message Edited by andrew_va on 08-09-2005 09:37 AM

  • Dev Mgr

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    Posted August 9th, 2005 14:00

    You can use dynamic disk to merge them by striping them, tho I personally am not a big fan of dynamic disks as it adds a layer between the OS and the storage space and if for whatever reason one of the LUNs is lost (double drive failure or other cause), all your data is lost.
  • andrew_va

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    Posted August 9th, 2005 21:00

    That's a good point re: Dynamic Disks. I am using 2000 Server and I think it supports Dynamic disks. I'll have to think about it...

    Thanks,
    Andrew
  • tommo666

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    Posted August 9th, 2005 21:00

    As Dev says, with dynamic disks you can stripe or concatenate(join at the end) the volumes. If you are using 2003 server. You could use DFS and lumps them into a shared pool.