[mythtv-users] Recent "pixelation" or "glitches" in recordings (HDHR related?)

[Tom Hayward]

On Tue, Apr 23, 2013 at 12:44 PM, Kenneth Emerson
<kenneth.emerson at gmail.com> wrote:
> I have six (6) three TB drives configured in a RAID6 partition of
> approximately 9TB.  On that RAID6 partition I have an LVM volume using XFS
> file system that contains all of my mythTV storage groups + music + photos +
> videos.  Also on these same six drives I have RAID1 partitions that have the
> OS and boot file systems (EXT4).  I have a separate SATA drive that contains
> my mythTV database.  The three TB drives are slow (WD Green drives - I think
> these are 5200 RPM).  Five of the drives are located on separate SATA ports
> on the motherboard and the sixth drive is in a RocketRaid external SATA
> enclosure.

That configuration will really kill your performance with seeks. Myth
works best with independent drives (but you've probably already heard
that). To mitigate your sub-optimal RAID configuration, configure a
big stripe cache and read ahead to minimize seeks:

blockdev --setra 16384 /dev/raidgroup/recordings
echo 16384 > /sys/block/md0/md/stripe_cache_size

(you'll need to redo this after a reboot)

See if this helps.


Tom