Re: RAID 0+1 vs RAID 5
From: Matty (mattyml_at_bellsouth.net)
Date: 05/30/04
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Date: Sun, 30 May 2004 09:52:36 -0400
On Sat, 29 May 2004 18:09:40 +1000, noone wrote:
> I have the ff setup:
>
> Solaris 8
> DiskSuite 4.2.1
>
> 1) Active database on a Sun Enterprise 3500 with dual A1000 disk arrays.
> Disks inside the array are stripped using hardware RAID 0 in the A1000.
> Then one A1000 is a mirror of the other, for RAID 1 mirroring using
> Solstice DiskSuite.
> Each array connected to separate SCSI controllers ( QLogic PCI-SCSI cards ).
> This setup has saved us a couple of times, when disks in the array would
> be reported as "Needs Maintenance" by DiskSuite,
> because the other half of the mirror in the other array is still working.
>
> Questions:
> How does Solstice DiskSuite, and Solaris itself, behave in the event of :
> 1a) a failure on the SCSI controller ( the QLogic PCI-SCSI card )
> 1b) a failure on the A1000 array itself, e.g. backplane, etc.
>
> Will DiskSuite still keep working in that, it will just ignore reading
> and writing to the failed array ?
Yes, When Solaris attempts to write to a path, enclosure or disk that
has failed, it will offline the device after X events and a retry
interval (I think I read this on docs.sun.com). Since the I/Os never
complete successfully, the OS will never get an ACK back from the SCSI
request.
> Or will it timeout, crash, panic ?
Nope. The whole point of mirroring across controllers/enclosures is to
avoid downtime when a catastrophic evvent occurs.
>
>
>
> 2) Standby database on a 280R with dual 3310 disk arrays.
> Now currently debating with the disk arrays in the 3310 should be
> configured similar to the A100s .. OR
> go RAID 5 on each array, and leave one disk on each array as a global
> hot spare.
> This also allows us with a lot of free disk space.
>
> I guess the deciding factor whether I should go RAID 5 vs. RAID 0 + 1
> will rely on the answer
> to my DiskSuite questions [1a] and [1b].
>
> If DiskSuite crashes, timeouts, panic, etc ... then there is really no
> point with the mirroring between
> two arrays with DiskSuite anyway.
>
>
>
> Any thoughts / suggestions ?
>
> Does RAID 5 hot spares replacing failed drivers work well with raw
> partitions ?
>
> Thanks
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