On Thu, 3 Feb 2000, Thomas Waldmann wrote:
> Hi Glenn,
>
> > > is performance. We have yet to get s/w RAID to perform any faster than
> > > 25MB/s (according to Bonnie) in any configuration or RAID level.
>
> > 25MB/s ?
> > Ive personally gotten 37MB/s with 3 quantum ide drives in raid0 mode,
> > each drive on its own channel.
>
> Maybe he is rather talking about RAID5 (and maybe SCSI). I also was a bit
> surprised as throughput seems to be limited to 25MB/s on my system (I already
> posted a mail on this topic some months ago).
>
> I had tried 4 * IBM DDRS 9GB on 2 UW SCSI channels: 25MB/s RAID5 (dual
> celeron 500 system, bonnie block read and write).
>
> I also had tried / am trying 4 * IBM DNES 9GB UW on 2 UW channels: this also
> gives 25MB/s, same system (read and write).
>
Here my results with 6 * IBM DNES 9GB U2W (4K blocksize):
-------Sequential Output-------- ---Sequential Input-- --Random--
-Per Char- --Block--- -Rewrite-- -Per Char- --Block--- --Seeks---
5 768 6582 97.6 38862 61.6 17510 51.0 7497 96.3 41476 30.5 346.0 5.5
6 768 6575 97.4 39471 60.1 15493 44.2 7577 97.3 40808 33.3 371.9 6.3
7 768 6625 97.6 40965 59.9 14219 40.3 7592 97.7 42571 35.9 271.1 4.9
8 768 7121 99.8 72177 73.5 21740 49.5 7711 97.9 64926 45.6 265.8 3.8
5) Software Raid 5 on one Adaptec U2W (chunksize=64 stride=16) 2.2.14
6) Software Raid 5 on one Adaptec U2W (chunksize=32 stride=8) 2.2.14
7) Software Raid 5 on one Adaptec U2W (chunksize=8 stride=2) 2.2.14
8) Software Raid 0 on one Adaptec U2W (chunksize=4) 2.2.14
Have you used the stride option when creating the filesystem and what
blocksize are you using?
> The strange thing: measured individually, these DNES HDDs give about 50% more
> throughput than DDRS (bonnie), but RAID5 throughput doesn?t change
> significantly.
>
> I?m still trying to get why this is like that. Looking at the 2 UW channels
> with 2 * 40MB/s and at a single drive rate of about 15-18MB/s, there should be
> more throughput possible.
>
What board are you using and is the controller onboard?
> > I think you should be able to get better than 25MB/s without too much
> > problem.
>
> I?m using an AIC7895 dual UW SCSI controller, 2 drives on each channel.
>
> What could I do more to optimize throughput ?
>
Read the excellent howto from Jakob OEstergaard!
http://ostenfeld.dk/~jakob/Software-RAID.HOWTO/Software-RAID.HOWTO.txt
Holger
