[mythtv-users] Software RAID problems - the unspoken mythtv problem?

David Ellis david at ellisonline.ca
Sat Jan 7 16:41:47 UTC 2006


I have 1.5tb in 300gb drives in a Raid 5 configuration. This is my MythTV
video directory. My record for simultaneous recordings was 5 (1xfoot ball
game, 1xSG1,1xSimpsons,1xSouth Park, and 1xMovie). All recordings were fine,
spread among 2xPVR 250's, 2xHD3000's, and 1xMercury TV Tuner.

I suspect you may have one of the following issues (please note, my setup
worked out of the box - without tweaks).

1) The filesystem I use on the raided mount point is "xfs" - what have you
chosen?

2) Are your drives more or less the same make/model and speed? Mine are
literally identical. 

3) Is your motherboard and CPU fast enough to handle multiple drives writing
at the same time? Mine is an AMD64, and I have plenty of Ram (about 4gb).
Not sure if this impacts you....but again it works for me.

>From the sounds of it, your problem really isn't a MythTV problem, but more
of a problem with multiple simultaneous writes to your raided volume. The
same issue would occur with MySQL, Postgres, or any other multithreaded
managed storage software.

David

-----Original Message-----
From: mythtv-users-bounces at mythtv.org
[mailto:mythtv-users-bounces at mythtv.org] On Behalf Of David Bennett
Sent: Saturday, January 07, 2006 8:08 AM
To: Discussion about mythtv
Subject: [mythtv-users] Software RAID problems - the unspoken mythtv
problem?

hello everyone,

  I am quite perplexed! Every problem I have ever encountered with
MythTV has been happily solved (and quickly too!) with this forums
help.

My current problem seems to be different! This will mark the third
time I am asking, and I have yet to receive a response. I'm wondering
if this is the dark secret of mythtv, if I am the only one
experiencing it, or if people are as clueless as to how to solve it as
I am!

Quick rundown:

Recording two programs that start at the same time without RAID: No
problem! 1yr++ ok.
When I have software raid enabled on the Video drive (doesnt matter
the combination, 2 drives, 3 drives, raid 1 or 5) I cant start
recording two programs at once. One of them comes up as an empty file.

If I start them 1 minute apart, no problem.

Usually I just get an empty file and I find out with a "B - filesize"
in MythWeb. Sometimes I get a Thread catching error in
mythbackend.log. I am at a loss as what to do!

Is this a software Raid cache thing? Is there a setting I can tweak!?
Has anyone experienced this problem!!!

Any help would be very much appreciated.

thanks in advance
David
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