Date: Tue, 19 Sep 2000 08:58:06 -0700 From: Julian Elischer <julian@elischer.org> To: Marc Tardif <intmktg@CAM.ORG> Cc: freebsd-fs@freebsd.org, freebsd-hackers@freebsd.org Subject: Re: device timings Message-ID: <39C78D0E.7DE14518@elischer.org> References: <Pine.LNX.4.10.10009191138220.8544-100000@Gloria.CAM.ORG>
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Modern disks pack different ammounts of data on different
tracks.. (the outside tracks are longer right?)
so at a constant speed (rpm) outside tracks have more data passing
below the head per given time than teh inside tracks do...
this seems pretty normal to me..
Marc Tardif wrote:
>
> Considering the following disk configuration:
> ******* Working on device /dev/rwd0 *******
> parameters extracted from in-core disklabel are:
> cylinders=256 heads=132 sectors/track=63 (8316 blks/cyl)
>
> parameters to be used for BIOS calculations are:
> cylinders=256 heads=132 sectors/track=63 (8316 blks/cyl)
>
> Media sector size is 512
> Warning: BIOS sector numbering starts with sector 1
> Information from DOS bootblock is:
> The data for partition 1 is:
> sysid 165,(FreeBSD/NetBSD/386BSD)
> start 63, size 1937565 (946 Meg), flag 80 (active)
> beg: cyl 0/ sector 1/ head 1;
> end: cyl 232/ sector 63/ head 131
> The data for partition 2 is:
> sysid 0,(unused)
> start 1937628, size 58212 (28 Meg), flag 0
> beg: cyl 233/ sector 1/ head 0;
> end: cyl 239/ sector 63/ head 131
> ...
>
> Now considering the following timings done with dd, how come I get such
> different transfer rates (bytes/sec) for s1 and s2? I understand there
> should be a difference between the block and character interface, as shown
> in the first two timings, but why isn't the same difference shown for the
> last two timings?
>
> # dd if=/dev/wd0s1 of=/dev/null bs=8316b count=5
> 5+0 records in
> 5+0 records out
> 21288960 bytes transferred in 8.580486 secs (2481090 bytes/sec)
>
> # dd if=/dev/rwd0s1 of=/dev/null bs=8316b count=5
> 5+0 records in
> 5+0 records out
> 21288960 bytes transferred in 4.058639 secs (5245344 bytes/sec)
>
> # dd if=/dev/wd0s2 of=/dev/null bs=8316b count=5
> 5+0 records in
> 5+0 records out
> 21288960 bytes transferred in 6.066568 secs (3509226 bytes/sec)
>
> # dd if=/dev/rwd0s2 of=/dev/null bs=8316b count=5
> 5+0 records in
> 5+0 records out
> 21288960 bytes transferred in 6.015735 secs (3538879 bytes/sec)
>
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--
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( OZ ) World tour 2000
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