[mythtv-users] MySQL on SSD 99% Utilization

[Eric Sharkey]

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):

mythtered% iostat -d -x  2
Linux 2.6.37-rc7-amd64 (mythtered)      02/03/2011      _x86_64_        (2 CPU)

Device:         rrqm/s   wrqm/s     r/s     w/s   rsec/s   wsec/s
avgrq-sz avgqu-sz   await  svctm  %util
sda               0.03     3.59    2.96    5.38    80.54    72.11
18.29     0.34   41.18   0.38   0.32
sdb               0.93   162.57    6.02    4.36  1590.21  1334.83
281.89     0.25   23.95   8.37   8.68
scd0              1.05     0.00    0.03    0.00     8.27     0.00
246.90     0.00    9.97   7.06   0.02
sdc               0.01     6.19    1.86    0.26   103.96    51.58
73.33     0.29  136.94   1.97   0.42

Device:         rrqm/s   wrqm/s     r/s     w/s   rsec/s   wsec/s
avgrq-sz avgqu-sz   await  svctm  %util
sda               0.00     2.50    0.00    9.00     0.00    92.00
10.22     0.01    1.33   0.22   0.20
sdb               1.50   581.00   20.50   16.00  4756.00  4776.00
261.15     0.50   13.64   6.90  25.20
scd0              0.00     0.00    0.00    0.00     0.00     0.00
0.00     0.00    0.00   0.00   0.00
sdc               0.00     0.00    0.00    0.00     0.00     0.00
0.00     0.00    0.00   0.00   0.00

Device:         rrqm/s   wrqm/s     r/s     w/s   rsec/s   wsec/s
avgrq-sz avgqu-sz   await  svctm  %util
sda               0.00     0.00    0.00    0.00     0.00     0.00
0.00     0.00    0.00   0.00   0.00
sdb               0.50   611.00   10.50   14.50  2772.00  5004.00
311.04     0.48   19.04  10.56  26.40
scd0              0.00     0.00    0.00    0.00     0.00     0.00
0.00     0.00    0.00   0.00   0.00
sdc               0.00     0.00    0.00    0.00     0.00     0.00
0.00     0.00    0.00   0.00   0.00

Device:         rrqm/s   wrqm/s     r/s     w/s   rsec/s   wsec/s
avgrq-sz avgqu-sz   await  svctm  %util
sda               0.00     0.00    0.00    0.00     0.00     0.00
0.00     0.00    0.00   0.00   0.00
sdb               1.50   372.50   11.00   10.00  3280.00  3060.00
301.90     0.33   15.24   6.86  14.40
scd0              0.00     0.00    0.00    0.00     0.00     0.00
0.00     0.00    0.00   0.00   0.00
sdc               0.00     0.00    0.00    0.00     0.00     0.00
0.00     0.00    0.00   0.00   0.00

So I think something is seriously misconfigured on your system.

Eric