[mythtv-users] Live TV problem

[Gary Buhrmaster]

On Sun, Dec 14, 2014 at 9:42 PM, Mike Carron <jmcarron at starstream.net> wrote:
....
> I want to be sure I'm on the right track first. As I mentioned that device
> is an SSD and is plenty fast on various performance tests, that's why I tend
> to suspect something in my setup. Is there any performance issue with having
> /var/lib/mysql/mythconverg and /var/lib/mythtv/livetv on the same partition?

That would depend on your particular brand of SSD,
and how it manages synchronous requests.  Some
SSD's will lie about committing the data to the actual
flash, and return quickly, some will actually wait
until the write to flash is complete (which can take a
long time, depending on the particular SSD), and a
few (usually enterprise) drives have sufficient internal
power reserve to insure that the data will be written to
flash and can return quickly.  And some SSDs will
perform internal reclaim activity which can delay
requests (better ones perform such activity in the
background).

Since MySQL, in order to insure the integrity of the
database, will sometimes use synchronous requests,
sometimes you will experience issues (and note
that there are other file system operations that can
do synchronous requests, MySQL may just be a
canary).

Performance tests are (usually) truthful regarding
the capabilities of that drive running that performance
test.  They are, at best, only suggestive about how
the devices will perform in your particular environment.

Just to be sure, make sure the SSD is running in
AHCI mode, and the queue depth is reasonable.