Yea, im always keen to see results, ive been trying to understand
performance
issues with ide raid0 for a while.
In the HOWTO i remember that says raid0 can give "near linear" performance
increases, a few weeks ago i played with a 4 way ide raid0, and i max'ed out
at
about the same figures you got.
I think scsi has similar problems, but this is more likely to be due to
saturating the
scsi bus, i remember seeing some good figures (70MB/s) with dual scsi
channels,
cant remember the details too well though (scsi is too expensive for me to
play with).
Could it be that near linear performance is a bit unrealistic ?
Im not a raid guru, so i too would be interested in other discussion about
maximum
raid0 throughput.
>
> Hello folks,
>
> Due to too much coffee while diagnosing another problem... I found myself
> unable to sleep. So I did some ide raid0 benchmarks for everyone to mull
> over.
>
> [Note that I did these benchmarks with hdparm and not bonnie, as I
actually
> had a readable raid5 filesystem on this disk set. But if I played around
> with raidtab's and hdparm I could do some non-destructive benchmarking.
>
> I am running redhat-6.0+updates, linux kernel 2.2.12, with
> raid0145-19990824-2.2.11.gz and 2.2.12.uniform-ide-6.20.hydra.patch.gz.
The
> machine is an Abit-BP6, celeron 366, 128MB RAM. All of the disks tested
are
> Maxtor 90845D4 5400RPM disks, or a close relative. ide0-1 is an Intel
> PIIX4, ide2-7 are three PDC20246 controllers.
>
> All of these tests were conducted with one disk per channel except for
hdb1
> which is slave on the same channel as the boot disk (system was otherwise
> idel)
>
> First set of tests: RAID0, 4k chunk size, cpu clocked at 366Mhz.
> All hdparms reported:
> Timing buffer-cache reads: 128 MB in 1.67 seconds =76.65 MB/sec
>
> 2 disks (hdb1,hdc1) buffered disk reads : 24.24 MB/sec
> 3 disks (hdb1,hdc1,hde1) buffered disk : 31.37 MB/sec
> 4 disks (hdb1,hdc1,hde1,hdg1) bfr disk : 35.75 MB/sec
> 5 disks (hdb1,hdc1,hde1,hdg1,hdi1) disk : 31.68 MB/sec
> 6 disks (hdb1,hdc1,hde1,hdg1,hdi1,hdk1) : 32.82 MB/sec
> 7 disks (hdb,hdc,hde,hdg,hdi,hdk,hdm) : 31.84 MB/sec
> 8 disks (hdb,hdc,hde,hdg,hdi,hdk,hdm,hdo): 32.00 MB/sec
>
>
> Same system. same disks, clocked at 550Mhz:
> Timing buffer-cache reads: 128 MB in 1.07 seconds =119.63 MB/sec
>
> 2 disks (hdb1,hdc1) buffered disk reads : 24.81 MB/sec
> 3 disks (hdb1,hdc1,hde1) buffered disk : 31.84 MB/sec
> 4 disks (hdb1,hdc1,hde1,hdg1) bfr disk : 37.65 MB/sec
> 5 disks (hdb1,hdc1,hde1,hdg1,hdi1) disk : 37.87 MB/sec
> 6 disks (hdb1,hdc1,hde1,hdg1,hdi1,hdk1) : 35.96 MB/sec
> 7 disks (hdb,hdc,hde,hdg,hdi,hdk,hdm) : 35.16 MB/sec
> 8 disks (hdb,hdc,hde,hdg,hdi,hdk,hdm,hdo): 32.65 MB/sec
>
> Bonus test, one disk from each controller, clocked at 550:
>
> 4 disks (hdc1,hde1,hdi1,hdm1) bfr disk : 38.79 MB/sec
>
> Completely non-useful bonus test:
> 10 disk raid5 set, 2 channels contain both master and slave disks for the
> set. 128k chunk size, 550Mhz, running in degraded mode.
> Timing buffered disk reads: 64 MB in 3.73 seconds =17.16 MB/sec
>
> Any comments or thoughts? I don't run raid0 in production, so this is no
> bitch fest. But I was pretty deep into my raid setup, and I thought people
> might appreciate some numbers. I was surprised to see the throughput top
> out at four disks and then drop lower after that.
>
> Tom
>
>
>
>
