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List:       linux-390
Subject:    Re: To SHARE or NOT ... that is the question(2)
From:       Mark Post <mpost () novell ! com>
Date:       2009-06-22 16:47:07
Message-ID: 4A3F7D4B0200006D0007BF8B () sinclair ! provo ! novell ! com
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> > > On 6/22/2009 at 12:31 PM, Dave Jones <dave@vsoft-software.com> wrote: 
> Hi, Mark.
> 
> Mark Post wrote:
> > > > > On 6/22/2009 at 11:41 AM, Dave Jones <dave@vsoft-software.com>
> > > > > wrote:
> > -snip-
> > > The real problem is that z/VM does not virtualize FCP-attached disk
> > > like it can do for ECKD and FBA devices....the WWPN and LUN values
> > > are "real" ones, and can not be shared across virtual machines.
> > 
> > Of course they can be, otherwise clustering wouldn't be possible at
> > all.
> > 
> How so, then? What I mean here is that FCP attached SCSI devices can not
> be "shared" across virtual machines the way CP handles sharing of 3390
> DASD, via the LINK statement.

That's what EDEVs are for.

> CP is not involved at all when Linux guests, as near as I can
> tell.....if two or more Linux guests share the same real SCSI device
> (same WWPN and LUN), then it's up to the guests themselves to manage access.

Correct, and that's a very well known and understood technology, whether using direct \
access by all systems involved or iSCSI.


Mark Post

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