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Re: [zfs-discuss] Re: ZFS - SAN and Raid

Subject: Re: [zfs-discuss] Re: ZFS - SAN and Raid
From: Gary Mills
Date: Tue, 19 Jun 2007 21:50:21 -0500
On Wed, Jun 20, 2007 at 11:16:39AM +1000, James C. McPherson wrote:
> Roshan Perera wrote:
> >
> >I don't think panic should be the answer in this type of scenario, as
> >there is redundant path to the LUN and Hardware Raid is in place inside
> >SAN. From what I gather there is work being carried out to find a better
> >solution. What is the proposed solution or when it will be availble is
> >the question ?
> But Roshan, if your pool is not replicated from ZFS'
> point of view, then all the multipathing and raid
> controller backup in the world will not make a difference.

If the multipathing is working correctly, and one path to the data
remains intact, the SCSI level should retry the write error
successfully.  This certainly happens with UFS on our fibre-channel
SAN.  There's usually a SCSI bus reset message along with a message
the failover to the other path.  Of course, once the SCSI level
exhausts its retries, something else has to happen, just as it would
with a physical disk.  This must be when ZFS causes a panic.

-Gary Mills-    -Unix Support-    -U of M Academic Computing and Networking-
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