[CentOS] Server Virtualization

Ross S. W. Walker rwalker at medallion.com
Wed Sep 19 21:22:14 UTC 2007

Mark D. Foster wrote:
> Paul Heinlein wrote:
> > On Tue, 18 Sep 2007, Flaherty, Patrick wrote:
> >
> >> If I had the time, I'd like to try using Xen with an 
> OpenSolaris ZFS
> >> iSCSI target as shared storage, but alas I do not have that time.
> >
> > FWIW, I've had good luck compiling and running the iSCSI target from
> > http://iscsitarget.sourceforge.net/ on CentOS 5. There 
> aren't all the
> > bells and whistles of ZFS, I suppose, but it's pretty simple to set
> > up. Also, given gigabit ethernet and a decent switch, its bonnie++
> > numbers aren't bad at all.
> >
> Apples and oranges, though.  iSCSI is networked block storage. It does
> not case what filesystem you lay on it. As someone who 
> learned this the
> hard way, it is not enough to have iSCSI to support live vm migration.
> If you are look to setup 2+ xen hosts and live migrate amongst them
> (known as vmotion in vmware-land) you need _shared_ storage 
> filesystem,
> and ext3 is not that nor is zfs. See
> http://en.wikipedia.org/wiki/List_of_file_systems#Shared_disk_
> file_systems
> for a list of FS that would suitable to lay on iSCSI for this purpose.

There is a configuration though that doesn't need a cluster file
system to perform live migrations and that is where the Xen VMs
write directly to a block device which is an iSCSI target.


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