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

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 Madden
Sr UNIX Systems Engineer / Office of Technology
Ivy Tech Community College of Indiana

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