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SubjectPlease comment on SCSI performance

Dear SCSI users,

my machine is a P133 with a plain 2.1.131 kernel. I was testing RAID0
performance of two of my drives with

time dd if=/dev/sd?? of=/dev/null bs=1024k count=128

to compare them to the speeds of the single drives.

To my surprise all my drives are showing the same slow performance.
All tests are repeated serveral times on an idle system. The SCSI host
adaptor is an Adaptec 3940 with aic driver version 5.1.4

The drives are:
Vendor: QUANTUM Model: LIGHTNING 730S Rev: 241E
Vendor: IBM Model: DORS-32160 Rev: WA6A
Vendor: IBM Model: DPES-31080 Rev: S31Q

The timings are:
sda1: real 0m36.719s user 0m0.010s sys 0m6.190s (3.48 MB/sec)
sdc2: real 0m24.953s user 0m0.010s sys 0m6.320s (5.12 MB/sec)
sdd2: real 0m31.088s user 0m0.000s sys 0m6.640s (4.11 MB/sec)
md0: real 0m35.522s user 0m0.010s sys 0m6.820s (3.60 MB/sec)

These values are much lower than previous kernel versions. I don't
have the numbers, but it's really true.

The RAID0 configuration is set up on two identical QUANTUM drives
mentioned above. I don't want to discuss RAID performance, but the
slower performace of all my drives.

If anyone could comment, if he/she is seeing a similar performance
decrease I would be pleased. BTW, the machine has 64MB RAM and the
timings do not differ that much from test to test, so I just posted
one result for each drive.

I know that dd is not a good benchmark and that I could play with the
RAID parameters, but it's the same setup I used for month and I just
wanted to point out the overall performance decrease, not only the
RAID performance.

Thanks for your comments,

Patrick


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