Re: Help with low raid5 performance

[Peter Kerwien <peter%kerwien.homeip.net@localhost>]

Moving the start of the partition to sector 128 did the trick!

And then did the following change:

START array
1 3 0

START disks
/dev/wd1e
/dev/wd2e
/dev/wd3e

START layout
32 1 1 5

START queue
fifo 100

Made a partition starting at sector 2048, created the filesystem with:

# newfs -O2 -b32k -s -64m /dev/rdk0

I then got the following result:

$ dd if=/mnt/vol1/pub/foo.mkv of=/dev/null bs=100m count=100
100+0 records in
100+0 records out
10485760000 bytes transferred in 89.019 secs (117792381 bytes/sec)

$ dd if=/dev/zero of=/mnt/vol1/pub/zero bs=100m count=100
100+0 records in
100+0 records out
10485760000 bytes transferred in 83.216 secs (126006537 bytes/sec)

Which is approx 120MB/s during read and 112MB/s during write! :-)

I still don't get all details or have mixed up some terms / settings

>> START layout
>> 64 1 1 5
> this says that the stripe width is 64 blocks...  With 2 data blocks and
> 1 parity block in each stripe, that gives you a total of 128 blocks of
> data in a stripe.
Isn't stripe width == the number of stripes you can write/read to/from
at the same time? I.e. a 3 disk RAID-5 has a stripe width of 3?

I thought 64 in my example, set the stripe size to 64 blocks, meaning
that the partition should be aligned to 64, 128, ... blocks.

BR,

/Peter