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

[C V <rayvittal-lists@xxxxxxxxx>]

I've been getting disappointing performance for file-backed disks mounted using 
tap:aio over an NFS mount. 
For example, bonnie++ reports 3 MB/s for block writes in the domU to
that
disk, but in dom0, bonnie++ reports 38 MB/s for that same mount. The
same domU can get 40 MB/s to the same filer using a phy: block device
over iSCSI .

It seems that 
1. tap:aio causes synchronous writes to the nfs mount (6 writes, wait for ack, 
write 6 more etc) as opposed to NFSv3 async write
2. Each synchronous write writes very small blocks (4K bytes vs max of 32K 
bytes)

Is there any configuration option to tweak this behavior to get 
better-performing async writes to the filer?

Thanks
--
CV

_______________________________________________
Xen-users mailing list
Xen-users@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-users