Date: Tue, 6 Jan 2004 13:20:55 -0500 From: "Derek Marcotte" <derek@cpainc.ca> To: "Mike Maltese" <mike@pcmedx.com>, <questions@freebsd.org> Subject: Re: Poor SCSI disk preformance Message-ID: <086401c3d481$d35e2ce0$0301a8c0@office.cpainc.net> References: <000201c3d461$eea71770$0301a8c0@office.cpainc.net> <012d01c3d47d$40fe8b50$f4f0a8c0@pcmedx.com>
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> I wouldn't say that dd is the greatest benchmarking tool. You
may want to
> try benchmarks/rawio.
I'll check that out just for kicks, but I _actually want_ to
write zeros to the drive first, not just as a benchmark. The
reasoning for this is that I'm trying to create a dedicated box
to format HDDs in parallel. I wish to first zero the drives to
make data recovery without an electron microscope difficult.
Then, to test for bad sectors I do a checksum of the number of
zero bytes written to disk, and then I read back from the disk
and compare checksums. Not exactly an extensive test, and perhaps
there is a verify option or trick in dd that I'm not aware of. I
think that this would catch any blatantly bad drives...
If not, there are 2 full disk operations that should be going
faster.
Actually, just for kicks:
# dd if=/dev/da0 of=/dev/null bs=128k &
[1] 1839
# iostat -K -w 1 da0
tty da0 cpu
tin tout KB/t tps MB/s us ni sy in id
1 42 64.00 607 37.92 1 0 1 0 98
0 43 64.00 222 13.87 0 0 2 0 98
0 43 64.00 223 13.92 0 0 0 2 98
0 42 64.00 224 13.98 0 0 2 0 98
0 43 64.00 222 13.86 0 0 3 0 97
0 43 64.00 223 13.92 0 0 1 2 98
0 43 64.00 223 13.92 0 0 2 1 97
0 42 64.00 223 13.92 0 0 3 0 97
0 43 64.00 223 13.92 0 0 1 0 99
Seems to give me the performance that I expect...
> Also, try monitoring diffferent types of transfers to
> and from another physical disk with iostat.
Actually, interestingly enough, when I copy a file, or do a
newfs_msdos I only get 0.06-0.89MB/s transfers, which is what
first tipped me off to the problems... Obviously less
acceptable...
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