[mythtv-users] Recording issues with I/O load

Stefan Lands e350notifier at alice.de
Fri Sep 23 09:58:52 UTC 2011

Well, thank you very much to Ian and Warpme for your help.

The raid used to be fully synchronized and speed seemed to be OK. But as
you pointed out correctly, this is not a mythtv related problem.

I tried a little bit more and disconnected the HDDs which contain the
raid. So PC was only running with one HDD containing OS and
mythtv-recording-directories. I produced heavy load to this disk
(recording, watching live-tv on a different frontend, nfs-transfer of
recorded mpgs via GB-LAN, doing md5sums of recording-directories) and
noticed no errors any more.

This lead me to the decision to take a quite radical step and kill the
raid5-array. Instead of this I build a simple group of these disks via
LVM as one big virtual disk. It took me 2 days to copy the old archived
recordings from external USB2.0 back to the computer.

Any further tests lead to no errors anymore. So the problem seemed to be
the raid itself. I don't know if this is a kernel-issue, or probably
related to the fact, that one of the raid-disks has 4kb-block size,
while the other ones have 512byte blocks. The partitions seemed to be
aligned properly. I couldn't find any IRQ-conflicts either.

So for now this case is closed. I reconfigured my backup-scripts to do
backups more frequently. The raid5 would have been quite a 1st degree
insurance against diskfailure. Sadly this doesn't work for me. Happily
the new backend now works as expected (except for the raid).

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