[mythtv-users] NFS + 3ware = slow

[Yeechang Lee]

James C. Dastrup <jc at dastrup.com> says:
> I just got a 3ware 7506-4 based on recommendation from this group.

See
<URL:http://groups.google.com/group/alt.comp.hardware.pc-homebuilt/msg/f8479484a5254f5d>
for details of my setup. I've made one key change to the configuration
since; see below.

Are you using hardware or software RAID?  LVM2?

> 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   <---- ??????

See <URL:http://www.gossamer-threads.com/lists/mythtv/users/169825>.
Bottom line: In my particular MythTV setup (and perhaps yours), Samba
is much preferable to NFS.

> 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.

I noticed the same behavior. In my case, getting rid of the LVM2 (and
yes, that meant moving about 2TB of data off the array to another,
rebuilding it, then moving the data back on; not fun) layer
*significantly* improved both remote and local write speeds on the
array.

Bill Peck wrote:
> Check out this bugzilla at Red Hat for the horror of these cards..
> https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=3D121434

The issue described in the Bugzilla entry is, while pretty awful for
those who experience it, one that only seems to bedevil RHEL users,
not Fedora as most MythTV home users will use.

-- 
Yeechang Lee <ylee at pobox.com> | +1 650 776 7763 | San Francisco CA US