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

[Paul Durrant <Paul.Durrant@xxxxxxxxxx>]

> -----Original Message-----
> From: Ian Jackson [mailto:Ian.Jackson@xxxxxxxxxxxxx]
> Sent: 02 March 2016 11:41
> To: Bob Liu
> Cc: Juergen Gross; xen-devel@xxxxxxxxxxxxx; jbeulich@xxxxxxxx; Roger Pau
> Monne; Paul Durrant; konrad.wilk@xxxxxxxxxx
> Subject: Re: [RFC PATCH] xen-block: introduces extra request to pass-
> through SCSI commands
> 
> Bob Liu writes ("Re: [RFC PATCH] xen-block: introduces extra request to
> pass-through SCSI commands"):
> > Do you know whether pvscsi can work on top of multipath(the device-
> mapper framework) or LVMs?
> 
> No, it can't.  devmapper and LVM work with the block device
> abstraction.
>

Google suggests you can use LIO to present an LV as a virtual SCSI LUN, in 
which case pvscsi should work.

  Paul
 
> Implicitly you seem to be suggesting that you want to use dm-multipath
> and LVM, but also send other SCSI CDBs from the upper layers through
> to the underlying SCSI storage target.
> 
> 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 ?
> 
> Ian.

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