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

[chris at cpr.homelinux.net]

On Sat, Jan 07, 2006 at 10:08:10PM +0900, David Bennett wrote:
> 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.

If there was a problem with the md block device or the filesystem 
handling simultaneous writes then you should be seeing lots of error 
messages in the system log.  In particular, ivtv would complain about 
buffer overruns.

This sounds more like a race condition in the Myth scheduler that's 
assigning both recordings to the same tuner when they start at the 
same time, but is bumping to the second tuner when there's a 
non-simultaneous overlap.

Did you update any of your software when you installed the RAID 
array?  If you make a new kernel then you may have changed to a 
different version of ivtv, and there was recently a device name 
change that requires you to wipe out your hardware settings and 
re-select the tuners.

If you have a non-RAID partition on your box then you should 
temporarily move your Myth recordings to the non-RAID partition and 
see if you can do simultaneous recordings.  That would give you a 
good indication of which way to go with this problem.

-- 
"When fascism comes to America, it will be wrapped in the flag and 
carrying the cross." - Sinclair Lewis (1935)