[dm-crypt] poor mysqldump performance

Milan Broz mbroz at redhat.com
Fri Feb 24 09:18:58 CET 2012


On 02/24/2012 12:59 AM, Tracy Reed wrote:
> On Fri, Feb 24, 2012 at 12:10:43AM +0100, Arno Wagner spake thusly:
>> I notice that you are using a really, really old kernel.
>> 2.6.18 is from end of 2006 or so. There were some
>> performance issues with the dm-layer, they might just
>> still be in this old version.

RHEL5 uses old dmcrypt code which is stable but has known
limitations.
The last change in RHEL was backporting suport for XTS mode.

Backporting of some performance changes is almost impossible
(if it easy I perhaps tried that long time ago).

Also please note that this is exactly where RHEL customer
requests helps - and there were no such requests.
So other things get priority.

So if you are using CentOS my advice is simple - try to upgrade
to CentOS6 and test it. It should be in some aspect better but still
database performance over dmcrypt can have problems.

Setting nr_request will not help btw, this is different problem.

Milan


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