[mythtv-users] Problem with latest run of optimize_mythdb.pl

[Stephen Worthington]

On Mon, 28 Dec 2015 13:05:02 -0700, you wrote:

>On Monday, December 28, 2015 01:51:19 PM Stephen Worthington wrote:
>> 
>> Check the free space on your drives.  One reason for
>> optimize_mythdb.pl crashing like that with the *.tmm files open is if
>> it runs out of space writing the *.tmm file, or another temporary file
>> while the *.tmm file is big.  Since recordedseek is normally larger
>> than the rest of the database put together, that is the table it will
>> crash on if the space is too low.
>
>Just how robust is MySQL at handling a major table rewrite like this on a live database? I see it's available in 0.27.5 and I wonder if I have to alter the twice-weekly cron-and-forget way I use it now (without the defraggng) or I can just drop it in and it will play nice with an active backend that might be recording at any time of the day.

Too heavy activity on the system drive or in the database (I am not
sure which) can cause bad recordings.  I currently have one DVB-T
recording that happens regularly during my database optimise time, and
it has recorded with gaps in it three times out of five in the last
seven days.  This did not happen before I started using the updated
optimise script that does defragmentation on the big tables.  I am
saving up for an SSD drive.  However, my database is huge compared to
most people - 14,340 recordings!  Today's compressed backup is
898,810,192 bytes.  The recordedseek .myd and .myi files are 2.9
Gibytes each.  For most people with smaller databases, there is
normally not a problem with the optimise or backup processes happening
at the same time as a recording, especially if the recording is going
to a different hard drive.

I also can not afford to turn off the defragmentation, as that causes
some long delays to happen in mythfrontend.  However, I suspect that I
could turn off defragmentation in the daily optimise cron job and only
do it manually when needed, so I could choose a safe time to do it
when there is an hour without recordings.  I have not experimented
with that yet.