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

[mark delfman <markdelfman@googlemail.com>]

We dont use 10 ports, we use 8 ports > 36 port expander. The 8 ports
act as a single wide port.

We are hitting a performance limit of circa 1.6 - 1.9GBsec regardless
of number of drives, so it max's at around 8 / 9 drives (with 15K).
RAID6 around 900MBsec i recall.  We expect more with emerging
expanders.

We were hoping to use DM MPIO to increase performance using multiple
cards and paths, but MPIO at best matches performance of a single
card, most likely pulls it down.... but this is a different topic i
guess.

XFS in the past has often increased performance - not allows on simple
sequential writes, but FS's are a lot better at intelligently caching
data... so I am very keen to help in whatever way i can to resolve the
FS > MD performance problem.

Thanks again.... Mark


On Tue, Oct 13, 2009 at 3:30 PM, Asdo <asdo@shiftmail.org> wrote:
>
>> On Tue, Oct 13, 2009 at 2:12 PM, mark delfman
>> <markdelfman@googlemail.com> wrote:
>>
>>>
>>> We upgrading mainly because of support for the emerging LSI SAS2 cards
>>> (which we are beta testing now)
>>>
>
> What is this LSI SAS2 card you have with 10+ ports? The only 10+ ports LSI
> card I see is the 84016E and it is a SAS1.
>
> You say the driver for such card is included in the vanilla kernel at
> 2.6.30? That would be very nice... I grepped the 2.6.31 kernel source for
> LSI cards but I can't find device strings such as 84016E ...
>
> Thank you
>