Re: Linux Software RAID 5 Performance Optimizations: 2.6.19.1: (211MB/s read & 195MB/s write)

[Justin Piszcz <jpiszcz@lucidpixels.com>]

On Fri, 12 Jan 2007, Al Boldi wrote:

> Justin Piszcz wrote:
> > RAID 5 TWEAKED: 1:06.41 elapsed @ 60% CPU
> >
> > This should be 1:14 not 1:06(was with a similarly sized file but not the
> > same) the 1:14 is the same file as used with the other benchmarks.  and to
> > get that I used 256mb read-ahead and 16384 stripe size ++ 128
> > max_sectors_kb (same size as my sw raid5 chunk size)
> 
> max_sectors_kb is probably your key. On my system I get twice the read 
> performance by just reducing max_sectors_kb from default 512 to 192.
> 
> Can you do a fresh reboot to shell and then:
> $ cat /sys/block/hda/queue/*
> $ cat /proc/meminfo
> $ echo 3 > /proc/sys/vm/drop_caches
> $ dd if=/dev/hda of=/dev/null bs=1M count=10240
> $ echo 192 > /sys/block/hda/queue/max_sectors_kb
> $ echo 3 > /proc/sys/vm/drop_caches
> $ dd if=/dev/hda of=/dev/null bs=1M count=10240
> 
> 
> Thanks!
> 
> --
> Al
> 
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> 

Ok. sec