Re: xfs > md 50% write performance drop on .30+ kernel?

[mark delfman <markdelfman@googlemail.com>]

A little more information which I ‘think’ seems to point at MD.....

Creating an EXT3 FS on an MD RAID also shows a circa 50% performance drop.
We have tried a multitude of RAID options (raid6/0 various chunks etc).

Using a hardware based raid XFS / EXT3 shows no performance drop
(although the hardware raid is significantly slower than MD in the
first place)

We are happy to keep testing and offering anything that could be
useful, we are just a little stuck thinking of anything else to do....




On Tue, Oct 13, 2009 at 2:33 AM, Christoph Hellwig <hch@infradead.org> wrote:
> On Mon, Oct 12, 2009 at 05:58:20PM +0100, mark delfman wrote:
>> Hi... in recent tests we are seeing a 50% drop in performance from
>> XFS>MD on a 2.6.30 kernel (compared to a 2.6.28 kernel)
>>
>> In short:  Performance to MD0 direct = circa 1.7GBsec (see below), via
>> xfs circa 850MBsec.  On previous system (2.6.28) there was no drop in
>> performance (in fact often an increase).
>>
>> I am hopefully that this is simply a matter of barriers etc on the
>> newer kernel and MD, but we have tried many options and nothing seems
>> to change this so would very much appreciate advice.
>
> Did barrier support for RAID0 got introduced in 2.6.30?
>
>
--
To unsubscribe from this list: send the line "unsubscribe linux-raid" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html