[mythtv-users] NFS + 3ware = slow

[James C. Dastrup]

I just got a 3ware 7506-4 based on recommendation from this group.
I'm having problems with writing to the RAID-5 array over NFS.
Here's some averaged samples using the cp command:

Samba (reading): 20 MB/s
Samba (writing): 20 MB/s
NFS (reading): 40 MB/s
NFS (writing): 4 MB/s   <---- ??????

Also interesting, the first 500 MB of data when writing over NFS
goes at about 50 MB/s, and then it slows to a crawl. RAID-5 array
is formatted JFS. CPU stays low on both machines. I've tried endless
amounts of mount options: sync,async, rsize=[1042-32768], 
wsize=[1024-32768], lock, nolock, hard, soft, intr, tcp, udp, 
nfsvers=33, etc. iperf is showing a raw transfer rate of 66 MB/s.

Has anyone seen anything similar? Does anyone know any debugging
tools or commands so I can see exactly where the slowdown is
occurring?