[mythtv-users] High IO activity during recording

Thomas Börkel thomas at boerkel.de
Sun Nov 30 16:51:49 UTC 2014


Hi,

one of my systems does most of the time very heavy IO activity during
recording, meaning that the disk is making noises and the LED is
flickering like hell. Every now and then, activity slows down and then
raises again shortly after.

My other system can record 4 shows concurrently with very little
visible/hearable disk activity.

I am at the moment testing recording the same 2 HD shows on both systems
(no commflagging) and the difference in activity is pretty big.

But the thing is, the 2 systems are pretty similar.

System 1 (low activity):
- AsRock mainboard, Core i5 Ivy Bridge
- SSD for system (deadline), 3 TB WD RED for recordings (cfq)
- kernel 3.14.16

System 2 (high activity):
- AsRock mainboard, Core i5 Sandy Bridge
- SSD for system (deadline), 4 TB WD RED for recordings (cfq)
- kernel 3.16.5

Both recording partitions are XFS with noatime,nodiratime. Both disks
are using udma6.

I see only mythbackend threads at the top when using iotop (2 MB/s total
disk write).

I also tried IO scheduler noop and deadline with no visible difference.

Is there anything in MythTV or in the kernel config, I can possibly
configure, like IO buffer size?

Thanks!

Regards,
Thomas



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