[mythtv-users] newbie just starting up mythbuntu

[Tom Hayward]

On Sat, Jan 28, 2012 at 18:58, David Sims <simsdw56 at comcast.net> wrote:
> Thanks Nick,
>
> Yeah...I plan on doing mirrored terabyte drives in the future and even
> perhaps raid 5.
> Just not there yet and want to experiment a little with this software.
>
> Will take a look at those logs and see what I find.

My only Myth storage group is an lvm partition on a 3-drive RAID-5
array. This is a BAD IDEA. 3 simultaneous recordings, commercial
flagging, and add in an occasional transcode operation and the array's
IO capability will be maxed out (it's the seek times that get you). I
occasionally get recordings with corruption that looks like poor
signal quality, but it correlates perfectly with a transcode
operation.

The best practice (that I will be migrating to eventually) is to keep
multiple drives independent and add them all to a storage group.
Myth's storage group scheduler will balance recordings between disks
to mitigate any IO bottleneck.

http://www.mythtv.org/wiki/Storage_Groups#Storage_Group_Disk_Scheduler

I've mitigated my own IO problems by throwing tons of memory at the md
array, both for the md write cache and the normal Linux read cache. It
would have been a lot easier to use independent drives for Myth and
leave the RAID-5 for my more valuable personal data.

Tom