Ubuntu 10.04 LTS disk write latency on VMWare 5.1

Hello, we've had this nagging performance issue on our performance benchmark
rack since installing Ubuntu 10.04 LTS OS on it. We've narrowed it down to a write latency issue when writing to the 12-disk array on the DL-380. The write latency on Ubuntu almost 10 times worse the amount seen with Solaris OS.

In a typical 1/2 hour load traffic run we'll get these results:

VMWare 5.1 on a HP DL-380 w/12-disk array
"Virtual Disk Perf Chart"
Solaris OS (ZFS):
Write Latency Max: 40 msec Average: 6.1 msec

Ubuntu OS (ext4):
Write Latency Max: 296 msec Average: 54 msec

The HP DL-380 The 12-disk array is configured as a single LUN RAID1+0 with a total capacity of 3.27TB. The Ubuntu is provisioned to use about 1.4TB of this for writing objects during the load test. The disk file system is currently configured with ext4, noatime.

Has anyone else experienced really bad write latency running Ubuntu OS in VMWare?

What is the preferred disk file system people are using for performance on Ubuntu OS? Has anyone had better luck running XFS or even ZFS file systems?

Thanks

Gary