[clug] iSCSI and shared filesystems

Steve Walsh steve at nerdvana.org.au
Thu Apr 22 20:50:35 MDT 2010

Steve Jenkin wrote:
> Anyone using an iSCSI back-end and sharing filesystems across multiple systems?
> I want to run a database (Postgres of MySQL) as a XEN guest and be able to live 
> migrate to another host.
yup, I've done that with a Xen VM running on an iSCSI export shared 
across a pseduo-cluster of machines
> Strongly prefer using simple techniques, like NFS.
> We are looking at buying storage appliances and what we can afford come with iSCSI.
Doing it with NFS has issues, iSCSI is much nicer
> Will a XEN guest Just Work with iSCSI to a back-end?
> [Two volumes, one for Data and one for Logs. backup/restore separately if needed]
> Will the live migration of the "DB in a VM" from host to host with iSCSI 
> mounted Filesystem (I'd prefer ext3) Just Work as well?
Edit config file appropriately, then use xm migrate <vm name> on machine 
B to grab a VM from machine A. provided both machines can see hte config 
file and the image/LVM backend, it "Just Works".
> For extra credit, can I NFS export the DB filesystems out of the DB-in-a-VM and 
> have it work seamlessly over the Live Migrate?
> [The IP number has to go with the VM]
Ugly, and dangerous, but the whole idea of migrating VM's is that the 
only that changes is the host it's running on (ala ESX migrate.

For those "not in the know", I'm currently packing up in Melbourne to 
come back to Canberra, so once I'm settled I'm happy to give a CLUG talk 
on the matter, or, if it's more pressing, Catchup over a coffee or a 
beer and explain the way it works.

Steve Walsh, RHCE
Some random guy who does things with linux and conference networks

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