Hello.
I have been running mdraid->cryptsetup/LUKS->lvm->xfs on Ubuntu AMD64 with
RAID5 and now RAID6 for quite some time, dating back to 2.6.27. Around
2.6.32 I saw quite a bit of regression in write performance (probably the
implementation of barriers), 2.6.35 was acceptable, 2.6.38 was really
really bad, and 3.0 is like a rocket. Best of them all.
I'm talking about 10-20x in different in write performance on my workload,
in combination with the older kernels throwing me page allocation failures
when the write load gets high, and also quite often the machine would just
freeze up and had to be rebooted.
With 2.6.38 I was down to 6-10 megabyte/s write speed, whereas 3.0 seem to
give me 100+ megabyte/s with the exact same workload, I've seen up to 150
megabyte/s writes at good times. This is on a box with AES-NI, so the
crypto is not the limiting factor.
I have from time to time sent out an email regarding my page allocation
failures, but never really got any takers on trying to fault find it, my
tickets with ubuntu also never got any real attention. I haven't really
pushed it super hard with 3.0, but I've thrown loads at it that would make
2.6.38 lock up.
Just wanted to send in this success report that this finally seem to have
seen some really nice improvements!
--
Mikael Abrahamsson email: swmike@xxxxxxxxx
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