Very low disk performance on 5.x

[Steven Hartland]

----- Original Message ----- >
> Raw read:
> /usr/bin/time -h dd of=/dev/null if=/dev/da0 bs=64k count=100000            
> 100000+0 records in
> 100000+0 records out
> 6553600000 bytes transferred in 32.028544 secs (204617482 bytes/sec)
>        32.02s real             0.02s user              2.73s sys

Out of curiosity just recreated the array with a 64K stripe ( the default )
/usr/bin/time -h dd of=/dev/null if=/dev/da0 bs=64k count=100000     
100000+0 records in
100000+0 records out
6553600000 bytes transferred in 61.246992 secs (107002806 bytes/sec)
        1m1.24s real            0.06s user              2.83s sys

/usr/bin/time -h dd of=/dev/null if=/dev/da0 bs=128k count=50000
50000+0 records in
50000+0 records out
6553600000 bytes transferred in 59.532993 secs (110083496 bytes/sec)
        59.53s real             0.00s user              1.86s sys

And a 32k stripe:
/usr/bin/time -h dd of=/dev/null if=/dev/da0 bs=64k count=100000
100000+0 records in
100000+0 records out
6553600000 bytes transferred in 41.947912 secs (156231853 bytes/sec)
        41.94s real             0.04s user              2.80s sys

So here the smaller the stripe the higher the transfer rate.
Some RAID0 results:
64k stripe:
/usr/bin/time -h dd of=/dev/null if=/dev/da0 bs=64k count=100000
100000+0 records in
100000+0 records out
6553600000 bytes transferred in 59.255960 secs (110598158 bytes/sec)
        59.25s real             0.04s user              2.52s sys

32k stripe:
/usr/bin/time -h dd of=/dev/null if=/dev/da0 bs=64k count=100000
100000+0 records in
100000+0 records out
6553600000 bytes transferred in 39.402059 secs (166326333 bytes/sec)
        39.40s real             0.00s user              2.96s sys

16k stripe:
/usr/bin/time -h dd of=/dev/null if=/dev/da0 bs=64k count=100000
100000+0 records in
100000+0 records out
6553600000 bytes transferred in 31.954544 secs (205091332 bytes/sec)
        31.95s real             0.04s user              2.73s sys

Conclusion from this is that at 16K stripe size RAID5 is identical read
performance of RAID0 which is what I would expect.

    Steve


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