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Re: Problem with file system on iSCSI FileIO

To: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Subject: Re: Problem with file system on iSCSI FileIO
From: Richard Sharpe <realrichardsharpe@xxxxxxxxx>
Date: Fri, 24 Sep 2010 08:10:51 -0700
Cc: Slawomir Nowakowski <slawomir.nowakowski@xxxxxxxxxx>, Artur Piechocki <artur.piechocki@xxxxxxxxxx>, xfs@xxxxxxxxxxx, Ryszard Stawiarski <ryszard.stawiarski@xxxxxxxxxx>, "??ukasz Wittig" <lukasz.wittig@xxxxxxxxxx>
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On Fri, Sep 24, 2010 at 12:55 AM, Christoph Hellwig <hch@xxxxxxxxxxxxx> wrote:
> On Thu, Sep 23, 2010 at 04:58:47PM +0200, Slawomir Nowakowski wrote:
>> iSCSI FileIO is using struct file that serves it as block level
>> device via iSCSI technology:
>> http://en.wikipedia.org/wiki/ISCSI
> Thanks, I know ISCSI very well.  But what is "iSCSI FileIO" ?  The above
> sounds like it's an iscsi target, is that correct?
>> There are RAID level 6 unit on the Areca RAID controller (1680). On
>> the unit is created a volume group. In the volume group we have
>> several logical volumes. The iSCSI FileIO volume is mounted and the
>> file (lun) is served via SCST target as iSCSI LUN.
>> We have checked RAM with memtest+ and verified RAID unit health and
>> no issues were found.
> I still can't make any sense of the actual setups.
> The above seems to be the backend storage.  Then there's SCST somewhere
> in which is in a out of tree kernel module.  And then you use XFS
> somewhere.  Please provide a full description of the setup.

Sounds like iSCSI-SCST to a vdisk_fileio on a file under xfs on a LUN
on the Areca RAID controller ...

Does sound awfully complicated. Why not just serve the LUNs from the
Areca directly? SCST allows you to do that. xfs is awesomely fast, but
it is just adding overhead here.

Richard Sharpe

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