Re: [Xen-users] Disk images

[Stephan Seitz <s.seitz@xxxxxxxxxxx>]

Am Montag, den 09.07.2012, 10:01 +0200 schrieb Agustin Lopez:
> Hello!
>
> We are planning to migrate our iSCSI installation (LUN based)  to one NFS installation (based in images).
> iSCSI offers great performance, but we have many dom0s and domUs and the management is difficult
> (many LUNS, many multipath messages, ...).
>
> (We are using Debian Wheezy with Xen 4.1.2)
>
> I have some questions:
>
> -What formats of disk images support Xen? I have not found support for qcow2, yes for HVD and raw.
> -Can anyone recommend a image over the other? Performace, stability, chars, ...
> -Anybody have tryed NFS modules from NetAPP or EMC  ?

the time, we integrated an emc vnx to our virtualization infrastructure, we've also tested file-based images exported on an nfs share
which was provided by an emc datamover unit. that unit was backed by an identical fc lun than other hosts connected via fc. that way,
we had a direct view to the raw i/o capacity. indeed, nfs was limited to 1GBit/s ether, but on a dedicated link and only mounted by one host.
nic and switch ports used for that nfs test had been set to 9k frames, nfs and tcp/ip parameters optimized for that particular link.
nfs performance was nice for file i/o on dom0, but at least moving benchmarking over to two loop-mounted images kept the host under
extreme load with quickly decreasing i/o.
we didn't went further inside "real" domU's because of that.

i'ld suggest, you're going to do your own benchmarks at your site, but i'ld not expect usable i/o.
dispite nfs, if you're lun management is going to be too difficult, have you ever thought of putting an ocfs2 or gfs2 (or maybe clvm) on top of your iscsi?

cheers,
stephan




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