[mythtv-users] MySQL on SSD 99% Utilization

[Mike McMullin]

On Thu, 2011-02-03 at 15:15 -0500, Brian Long wrote:
> On Thu, Feb 3, 2011 at 2:44 PM, Eric Sharkey <eric at lisaneric.org>
> wrote:
>         On Thu, Feb 3, 2011 at 11:40 AM, Brian Long
>         <briandlong at gmail.com> wrote:
>         > Is it generally a
>         > bad practice to put MySQL on a SSD?  I figured it would
>         provide a nice fast
>         > DB and keep my DB separate from my recording disks, but I
>         guess I was wrong.
>         
>         
>         I have my backend's MySQL db on an SSD, with the recordings on
>         a
>         magnetic disk, and I don't have anything like the problems
>         you're
>         seeing.  Moving the db to the SSD seems to have been a big
>         boost to
>         responsiveness when it comes to searching/scheduling new
>         recordings or
>         bringing up the guide data.
>         
>         One thing I have noticed with iostat is that it tends to
>         report
>         elevated numbers on its first invocation, which is why I
>         always give
>         it a repeat interval (usually 2 seconds) and watch until it
>         appears to
>         be at a steady state.
>         
>         I have comm flagging going on right now and here's what I see
>         (/dev/sda is my SSD):
>         <snip>
>         So I think something is seriously misconfigured on your
>         system.
> 
> Yes, I didn't dig deep enough and it's not MySQL slamming my SSD; it's
> the mythbackend logging to /var/log which is also on my SSD.  I tried
> tuning MySQL and moving /var/lib/mysql to spinning disk and noticed
> the SSD was still 99% utilized.  Then I noticed my mythcommflag job
> was endlessly logging the following types of errors:
> 2011-02-03 15:10:43.547 AFD Error: Unknown decoding error
> 2011-02-03 15:10:43.564 [h264 @ 0x37412f7ec0]decode_slice_header error
> 2011-02-03 15:10:43.583 [h264 @ 0x37412f7ec0]no frame!
> 2011-02-03 15:10:43.583 [h264 @ 0x37412f7ec0]get_buffer() failed
> (stride changed)
> 2011-02-03 15:10:43.604 [h264 @ 0x37412f7ec0]decode_slice_header error
> 2011-02-03 15:10:43.653 [h264 @ 0x37412f7ec0]no frame!
> 
> 
> Mythbackend seems to be DOS'ing my SSD!  :-)  I guess I need to dig
> into removing that job from the queue since mythcommflag doesn't like
> the recording.

  What about linking the log directory to one on the spinning disk?