RE: [Xen-users] xen 3.3 -> tap:aio performance over nfs

["James Harper" <james.harper@xxxxxxxxxxxxxxxx>]

> 
> I am mounting file-based disk images (tap:aio) ) for VM from a nfs
server
> (SATA, RAID 5) too. The link to the nfs server is a 1 G ethernet.
> The read and write performance is also bad, all around 10M/s. The
write
> size for the nfs client is set to 8K (I tested with different sizes,
like
> 16K and 32K, similar performance).
> Is there any way to optimize the disk-based VM performance? Currently
> there are 10+ VMs mounted to the nfs server and they include
webservers,
> OLTP, and Java application servers.
> 

To elaborate on my previous reply to the parent poster, do it a
different way. AoE and iSCSI are both protocols which are designed to
share a block device (or a file acting as a block device) between two
servers. It is designed with the sorts of things a server is going to
expect of a block device.

NFS is a filesystem, it is designed for exporting files, and takes care
of things like file locking and concurrency. It isn't designed to do
what you want to do with it, and so probably isn't going to perform
well.

AoE at least is really really easy to set up. Run vblade on your file
server to export the disk image, and use the aoe tools on your xen
server, and use tap:aio on the aoe disk device. If performance improves
then maybe look at iSCSI too, which is harder to set up but may give you
better performance still.

James


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