Re: Wierd lvm2 performance problems

[Eugene Vilensky <evilensky@gmail.com>]

Google brought up this bug https://bugzilla.redhat.com/show_bug.cgi?id=232843  .  The read-ahead values for LV are set to a much lower value than for a md, but can be adjusted in user-space (my understanding).

Regards,
Eugene Vilensky
evilensky@gmail.com

On Sat, Apr 18, 2009 at 5:25 PM, Sven Eschenberg <sven@whgl.uni-frankfurt.de> wrote:

Dear list,

I tried to create a PE+VG+LV ontop of a mdraid. For no obvious reason the lvm volume show extremely poor performance - The transferrates are as little as 30% of the rates on the md device itself.
In contrast creating a partition table ontop of the array gives nearly no performance impact.

Does anybody have the slightest idea, wht might be going wrong here?

Regards

-Sven

P.S.: I tried aligning the first PE in the VG with the mdraid chunk size, no difference whatsoever.

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