Re: [Xen-users] Re: Xen + SAN

[John Madden <jmadden@xxxxxxxxxxx>]

> I don't know about AOE but with ISCSI the problem I'm seeing is that if
> i create a volume group on the SAN there is no way to export that volume
> group.  I could export the device that the volume group was created on
> but then the host doesn't see that VG. I'm assuming i would need to use
> clustered LVM for that which i have been told to stay far away from.
> Another option was to carve out the LV's on the SAN and to export each
> LV to the initiators but still the problem is that the host assigns
> these luns to /dev/sd devices and there's no simple nice way to map them
> to who owns what disk.  Least not that I've found yet.  I'm fairly new
> to ISCSI though so maybe there's something I'm missing.
A != B.  Sure, scsi devices get assigned to each host in /dev but this 
has nothing to do with ownership.  In a cluster, you'd want them all to 
have "ownership" at a SCSI level... cLVM will handle LVM metadata change 
locking but still isn't strictly necessary.  (I've begun to move away 
from it for my clusters -- it's a /bitch/ and far more hassle than it's 
worth.)  For metadata changes, I pick a node and then run things like 
`vgscan` and `lvchange -ay` on the other nodes.  ClusterSSH makes this a 
breeze.  But that's beside the point: share your disks over iSCSI, SAN, 
AOE, or JBOD, it makes no difference.
John



--
John Madden
Sr UNIX Systems Engineer / Office of Technology
Ivy Tech Community College of Indiana
jmadden@xxxxxxxxxxx

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