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

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)

I can very loosely (based on very early testing and slightly different hardware) agree.

A couple of 2.6.27.19-78.2.30.fc9.x86_64 machines - 8GB RAM LSI SAS controller and 16 x WD RE3 750GB SATA md RAID6.

With stripe cache set to 16384, I see dd writes of 590MB/s.

Started testing a similar machine yesterday - 12GB RAM LSI SAS controller and 16 x WD RE3 1TB SATA md RAID6.

With stripe cache set to 16384, I see dd writes of around 290MB/s and when bumped up to 32768 (the maximum), it increases to 407MB.

Read performance is about the same as the older system - around 960MB/s.

Both systems are using XFS with an external journal.

As I say, early days - I've not compared scheduler etc. settings between kernels, but somewhatr disappointing.

Regards,

Richard