Ext3 and 3ware RAID5

[Joshua Baker-LePain]

On Sat, 15 Apr 2006 at 12:57pm, Sean O Sullivan wrote

> Alex Bligh wrote:
>> 
>> --On 15 April 2006 07:33 -0400 Joshua Baker-LePain <jlb17 at duke.edu> wrote:
>> 
>>>> No idea, but I suffer the same problem with a 9550SX-4 with SATA3
>>>> drives. I don't think ext3 is the problem as dd gives much the same
>>>> behaviour (you might want to try it). My reluctant conclusion is
>>>> that the 9550SX is just dog slow, which is why the drives are currently
>>>> sitting idle. I would love someone from 3ware to disprove this.
>>> 
>>> When ext2 is almost 2X faster than ext3 at writing, it points pretty
>>> firmly at something in the journaling code (IMO).  And a journaling FS
>>> can do decently with this hardware, as XFS also gets ~300MB/s writing.
>> 
> I had similar problems with 9500S-8, and searched about, and eventually found 
> some useful information.
> Try mounting the volume with the 'noreservation' option.

AFAIK, that bug was fixed in the most recent centos/RHEL kernel.  In any 
case, noreservation made no difference.

> Also, it is well worth your time setting 'blockdev'
> for example : blockdev --setra 20000 /dev/sde
> and this put this in /etc/rc.local

Yeah, I've already played around with blockdev a lot.  It made some 
difference, but nothing extraordinary.


-- 
Joshua Baker-LePain
Department of Biomedical Engineering
Duke University