[CentOS] RAID6 in production?
jlb17 at duke.edu
Thu Oct 20 15:00:58 UTC 2005
On Thu, 20 Oct 2005 at 9:43am, Aleksandar Milivojevic wrote
> Quoting Joshua Baker-LePain <jlb17 at duke.edu>:
>> Needless to say it's not giving me that warm fuzzy feeling. The one caveat
>> is that not all the members of my array were the same size -- one disk is
>> 180GB while all the rest are 160GB. I'm going to test overnight with
>> identically sized RAID members, but I also wanted to see if anyone else is
>> using RAID6.
> I was testing RAID-5 with identical disk drives. Got the same thing. If I
> attempt to access it while it rebuilds, sooner or later I get errors. If I
> reboot while it rebuilds, it doesn't start it after the reboot (forgot the
> actuall error message). I needed to manually kick it again using mdadm to
> force-start it. If it was root file system, the machine would probably fail
> boot completely. You might want to stick to your 3ware for now.
Wonderful. I'm testing RAID5 now, for which I had high hopes.
> BTW, any particular reason not to use hardware RAID on 3ware?
That was the initial plan. But I can't get anything even resembling
decent speeds out of them. These systems have 2 7500-8 boards in 'em (on
separate PCI buses). I had been running RH7.3 (!!) and XFS with the
boards in hardware RAID5 and a software RAID0 stripe across those, and
would get >100MB/s writes and >300MB/s reads. With centos-4 and ext3, I
was getting ~30MB/s writes and ~200MB/s reads. The reads I'd be OK with,
but the write speed is absurd. I tweaked all I could think of, but
nothing helped much.
Department of Biomedical Engineering
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