[mythtv-users] NFS + 3ware = slow

[bill peck]

On 3/11/06, James C. Dastrup <jc at dastrup.com> wrote:
>
> 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?



I owned a 3ware card at one time..  I ran it with 4 ide drives in a raid 0.
Worked great.  But...  Running in a raid 5 config is horrible..

Check out this bugzilla at Red Hat for the horror of these cards..
https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=121434

I now own a Promise Sata controller which cost me $40.00 and yes it uses my
CPU for raid 5 but at least I get great perfomance from it and I didn't
spend $300-$400 for a useless card.


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--

Bill Peck
http://www.pecknet.com
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