On Tue, 13 Oct 1998 [EMAIL PROTECTED] wrote:
> Hi all!
>
> I've been running raid-0 and linear modes on a disk array for some time. This
> works really well! (I guess you allready knew :)
>
> Now, I moved the disks (six quantum fireball 6 GB scsi on two ncr53c810 controllers,
> three disks on each), into another machine and wanted to run RAID-5 on them.
>
> The kernel which worked so well for me was 2.0.35 with md-tools 0.35.
> The new machine runs 2.1.125, and I use the raid-5 capabilities in that kernel
> unpatched. Furthermore, I use raidtools-0.41.
>
> I followed the instructions, and got a raid-5 array up running, or ``crawling''...
> mke2fs takes long time (I went away from the machine, so I don't have timings).
> Large writes almost hangs the machine. A ckraid takes 80 minutes. Bonnie on the
> array gave theese weird timings:
>
> -------Sequential Output-------- ---Sequential Input-- --Random--
> -Per Char- --Block--- -Rewrite-- -Per Char- --Block--- --Seeks---
> Machine MB K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU /sec %CPU
> 400 5286 92.3 107 16.8 3557 18.7 3104 48.9 11332 19.9 387.1 7.4
>
> What really pussles me is, that putc() seems to give good results, while block writes
> are unbelievably slow. I'm aware that raid-5 will always be slower than raid-0, but
> this is extreme.
Ouch.. 100KB/sec on block writes is indeed unusable; strange, as we
usually score very well on bonnie's block-writes.
Does it happen consistently on each run? Does one of the drives in the
RAID array also contains an active swap partition? Does it also happen
with a RAID set of 3, 4 or 5 rather than 6 disks on your system?
Gadi
>
> For reference, I tried setting up the array as raid-0 again. This time the machine
> stayed responsive, and behaved much like the old setup used to. Bonnie here gives:
>
> -------Sequential Output-------- ---Sequential Input-- --Random--
> -Per Char- --Block--- -Rewrite-- -Per Char- --Block--- --Seeks---
> Machine MB K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU /sec %CPU
> 400 5403 84.3 18576 35.6 6859 25.5 4787 74.3 15879 26.6 398.8 6.4
>
>
> What is wrong ? Is raid-5 really so inherently slow, and has to lock the machine,
> or am I missing something ? (The machine is a dual PII-350, I guess it should be
> able to calculate the parity fast enough)
>
> Furthermore, where can I get recent information about the raid tools ? I looked at
> some sites, but often they have missing links or ``last modified early 1997'' in
>them.
>
> Thank you very much.
>
> ................................................................
> : [EMAIL PROTECTED] : And I see the elder races, :
> :.........................: putrid forms of man :
> : Jakob �stergaard : See him rise and claim the earth, :
> : OZ9ABN : his downfall is at hand. :
> :.........................:............{Konkhra}...............:
>
>
