[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Old Index]
Re: Help with low raid5 performance
On 11/09/2010 06:44 PM, Juergen Hannken-Illjes wrote:
> On Tue, Nov 09, 2010 at 04:38:59PM +0100, Peter Kerwien wrote:
>> 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??
> You should try "block size == stripe size" to avoid read-modify-write.
> What throughput do you get from "newfs -b 32k ..."?
Thanks, I have now reformatted with:
# newfs -O2 -b 32k -s -64m /dev/rdk0
I'm now seeing speeds between 20-25MB/s per disk, i.e. approx 40-50MB/s
to the raid. Still much less than I expected. I was hoping for
~50-60MB/s per disk => >100MB/s to the raid.
I think I need more help.
Main Index |
Thread Index |