HVM disk I/O

["Aaron J. Grier" <agrier%poofygoof.com@localhost>]

xen 3.3 from pkgsrc on NetBSD-5/amd64

I have a raidframe RAID1 created under my Dom0 with a stripe size of 64k
(128 sector).  I get 100MB/s read/write on a filesystem with 64k block
size.  this makes me happy.

I exported the partition to the domU, and installed NetBSD-5.1 under a
domU HVM.  formatting a filesystem with 64k blocks and performing the
previous test yields 100MB/s reads, but only 35MB/s writes.

looking at iostat on the dom0, I see only 8k operations to the RAID.  is
this expected?  is xen unable to handle 64k I/O operations through the
virtualized hardware?

or should I just redo my RAID1 with 8k stripes and suck up the
performance loss, or would a domU be any better?

-- 
  Aaron J. Grier | "Not your ordinary poofy goof." | 
agrier%poofygoof.com@localhost