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

[Kenneth Emerson]

On Apr 23, 2013 3:24 PM, "Tom Hayward" <esarfl at gmail.com> wrote:
>
> 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

Thank you, Tom. I wasn't looking for (another) debate on the use of RAID
with mythTV. I understand that my setup isn't optimal, but until very
recently, it has been working fine. I was thinking something else has
happened/changed  and looking for others' experiences. Those delay writes
are fairly recent-- maybe I have a drive beginning to fail.  I will try
your suggestion and see if it helps. Even if I wanted to, breaking the RAID
array apart would be expensive and a lot of work.

--Ken E.
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