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Help with low raid5 performance


I'm testing a RAID-5 configuration with RAIDframe, but cannot get decent performance. I have read the following thread:

But cannot understand what I'm doing wrong. I'm experimenting with 3 x WD 500GB RE2 drives, which give approx. 55-60MB/s when using them as separate disks (measured with iostat during a file copy to the drive). But when setting up a RAID-5 configuration with all three drives, I'm seeing something between 10-20 MB/s. Never above 20MB/s. The latest setup I have tried is the following:

Raid configuration:

START array
1 3 0

START disks

START layout
64 1 1 5

START queue
fifo 100

So what I understand gives a stripe size of 64 sectors = 32kBytes. So now it is important that the partition on raid0 (my raid-5 device) is aligned with this. I have then created the following gpt:

# gpt show raid0
       start        size  index  contents
           0           1         PMBR
           1           1         Pri GPT header
           2          32         Pri GPT table
          34          30
          64  1953546015      1  GPT part - NetBSD UFS/UFS2
  1953546079          32         Sec GPT table
  1953546111           1         Sec GPT header

and the corresponding wedge:

# dkctl raid0 addwedge dk0 64 1953546015 raid0

and finally a filesystem with:

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

(In my case: block size = 16kB => fragment size = 2kB).

What important thing have I missed or done wrong??


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