[mythtv-users] MySQL on SSD 99% Utilization

Raymond Wagner raymond at wagnerrp.com
Thu Feb 3 17:43:50 UTC 2011

On 2/3/2011 12:37, Matthew McClement wrote:
> On 02/03/2011 05:27 PM, Raymond Wagner wrote:
>> On 2/3/2011 11:40, Brian Long wrote:
>>> The CPUs are doing almost nothing so it appears the MySQL updates
>>> being performed during a commflag are screwing with the SSD.  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.
>> Looking at reviews on the SSDNow V 30GB, the one thing that stands out
>> is awful random read/write performance.  Even still, it should be far
>> better than a disk drive is capable of.
> Anands benchmarks show the SSDNow V 30GB is the same speed as a
> Velociraptor at 4K random writes, which is pretty terrible for a SSD:
> http://www.anandtech.com/bench/Product/155?vs=182

That metric just looks wrong.  It looks like they're buffering writes to 
something other than the drive, and that something else is actually what 
is bottlenecking.  That's the only way to account for the discrepancy 
between reads and writes.  Measuring write buffer speed is meaningless 
unless that write buffer is battery backed and recoverable.

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