[mythtv-users] Suggestions for a partition structure

[Raymond Wagner]

On 10/21/2013 3:34 PM, Joseph Fry wrote:
>>   Putting your database on the same disk as your
>> recordings is already highly advised against.  Putting it as a mirrored
>> partition on a pair of recording disks would only exacerbate the issue.
> What issue is that.

MySQL performs atomic writes, and now with barriers being enabled by 
default, those atomic writes go straight to platter.  That means each 
write to the database is going to incur one write for the data, likely 
another write for the index, and several writes each for filesystem 
metadata.  Each of those means another seek on the platter.  With MPEG2 
recordings, you're typically looking at to seek table updates per second 
per recording, and by the time you're done, you've got a substantial 
chunk of throughput eaten up by seeks.

> I get the benefit of very fast reads against the DB due to
> there being 3 mirrors

Usually configuring MySQL to use more than the default (unconfigured) 
tiny chunk of memory is sufficient for that.