Re: [Xen-devel] [RFC PATCH] xen-block: introduces extra request to pass-through SCSI commands

[Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>]

Bob Liu writes ("Re: [RFC PATCH] xen-block: introduces extra request to 
pass-through SCSI commands"):
> On 03/02/2016 07:40 PM, Ian Jackson wrote:
> > I can't see how that could cause anything but pain.  In many cases
> > "the underlying SCSI storage target" wouldn't be well defined.  Even
> > if it was, these side channel SCSI commands are likely to Go Wrong in
> > exciting ways.
> > 
> > What SCSI commands do you want to send ?
> 
> * INQUIRY

... but why ?

> * PERSISTENT RESERVE IN
> * PERSISTENT RESERVE OUT
> 
> This is for Failover Clusters in Windows, not sure whether more
> commands are required.  I didn't get a required scsi commands list
> in the failover document.

So you want to be able to reserve the volume against concurrent
access ?  If you're using LVM, such a reservation should apply to the
LVM LV, not to the underlying physical storage device, clearly.  So I
think LIO [1] + PVSCSI might be what you want.

Ian.

[1] http://linux-iscsi.org/wiki/LIO

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