RE: [Xen-devel] [PATCH 0/6] pvSCSI (SCSI pass through) driver

["James Harper" <james.harper@xxxxxxxxxxxxxxxx>]

> Hi,
> 
> On Tue, 2007-10-30 at 19:39 +0900, Jun Kamada wrote:
> 
> Is this using the same syntax for HBA reservation that we used to
have,
> ie. simply enumerated using the scsi host number on the dom0?
> 
> If so, that is rather fragile.  The scsi host number can change from
> kernel to kernel depending on HBA driver probe order and PCI bus
> enumeration order.  It changes when hardware is rearranged.  And how
do
> we deal with migrate, when we'll need to select a completely different
> HBA on a different host?
> 
> Selecting the HBA by scsi host number is good enough for a
demonstration
> that the code works, but I don't think it's going to be robust enough
> for production deployment.
> 
> Also, has there been any progress towards exposing individual LUNs to
> the guest rather than a whole HBA?

People keep saying individual LUN... do they actually mean SCSI Target
devices? Splitting up devices on the same HBA should be reasonably
simple, but due to the way the scsi protocol works (AFAIK), splitting up
LUN's on a single SCSI device could be a bit trickier...

Or maybe LUN doesn't mean what I think it means in this case... my
understanding is:

HBA = Host Bus Adapter (eg a PCI SCSI adapter)
SCSI Target Device = one of the physical devices that sits on the SCSI
bus (eg a tape drive or a disk drive)
LUN (Logical Unit Number) = a sub unit of the SCSI Target Device, eg a
single disk drive in a RAID array, a tape device in an multi tape drive
autoloader, a CD ROM in a CDROM tower.

...

James

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