[mythtv-users] MySQL on SSD 99% Utilization

Matthew McClement mythtv at macker.co.uk
Thu Feb 3 21:35:03 UTC 2011

On 03/02/11 18:51, Raymond Wagner wrote:
> On 2/3/2011 13:46, Raymond Wagner wrote:
>> On 2/3/2011 13:38, Matthew McClement wrote:
>>> Eh? SSD's are significantly slower at writes than reads, especially if
>>> you're writing to a non-GC'd cell, which with how the Toshiba controller
>>> handles TRIM is entirely possible(GC isn't continuous but rather seems
>>> to be demand triggered). If you then add non-aligned sub-page sized
>>> writes, things can get bad pretty quickly.
>>> It's buffering and other tricks which make SSD's faster today over the
>>> early versions, rather than slower.
>>> And it's not like that result is an oddity. Just look at any benchmark
>>> for the early JMicron based SSDs to see SSDs that were often *slower*
>>> than hard disks at random writes.
>> That benchmark showed write performance on the velociraptor to be ~20x
>> that of the read performance.
> Make that ~3x.

Welcome to the world of NCQ and queue depths > 1.


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