On Friday 20 of December 2013, Kevin Richter wrote:
> >> $ cat /sys/block/md2/md/stripe_cache_size
> >> 256
> >
> > 256 is the default and it is way too low. This is limiting your write
> > througput. Increase this to a minimum of 1024 which will give you a
> > 20MB stripe cache buffer. This should become active immediately. Add
> > it to a startup script to make it permanent.
> > $ echo 256 > /sys/block/md2/md/stripe_cache_size
> > $ time cp -a /olddisk/testfolder /6tb/foo1/
> > real 25m38.925s
> > user 0m0.595s
> > sys 1m23.182s
> >
> > $ echo 1024 > /sys/block/md2/md/stripe_cache_size
> > $ time cp -a /olddisk/testfolder /raid/foo2/
> > real 7m32.824s
> > user 0m0.438s
> > sys 1m6.759s
> >
> > $ echo 2048 > /sys/block/md2/md/stripe_cache_size
> > $ time cp -a /olddisk/testfolder /raid/foo3/
> > real 5m32.847s
> > user 0m0.418s
> > sys 1m5.671s
> >
> > $ echo 4096 > /sys/block/md2/md/stripe_cache_size
> > $ time cp -a /olddisk/testfolder /raid/foo4/
> > real 5m54.554s
> > user 0m0.437s
> > sys 1m6.268s
>
> The difference is really amazing! So 2048 seems to be the best choice.
> 60GB in 5,5minutes are 180MB/sek. That sounds a bit high, doesnt it?
> The RAID only consist of 5 SATA disks with 7200rpm.
I wonder why kernel is giving defaults that everyone repeatly recommends to
change/increase? Has anyone tried to bugreport that for stripe_cache_size
case?
--
Arkadiusz MiÅkiewicz, arekm / maven.pl
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