Subject: Re: comparing raid-like filesystems
To: Antti Kantee , Jukka Marin <email@example.com>
From: Greg 'groggy' Lehey <firstname.lastname@example.org>
Date: 02/02/2003 12:59:04
On Saturday, 1 February 2003 at 11:08:32 +0200, Antti Kantee wrote:
> On Sat Feb 01 2003 at 10:04:25 +0200, Jukka Marin wrote:
>> I have no experience of the RAID controllers, but I'm not particularly
>> happy with the NetBSD RAIDframe implementation. I bought fast disks,
>> configured RAID - and found out that RAID drops the performance to a
>> fraction of that of the disks.
>> I don't know why, because when RAID is 100% busy, CPU load is almost
>> zero and the disk load 25% or so. It's like if RAIDframe had some
>> usleep() calls in the code to make things go slower..
> What's your stripe unit size? I also was suffering from inexplainable
> slowness until I dropped the stripe unit size to 16 sectors. Before that
> my RAID5 gave something like 5MB/s write speeds, now it's giving more
> than 25MB/s.
That's puzzling. Normally small stripes decrease performance because
they cause more I/O (more transfers go over a stripe boundary). It
suggests that there is some deficiency in the way RAIDframe handles
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