Disk Xfer Rates vs Bus Speed

[Terence Kelleher]

In article <20606 at sgi.SGI.COM> markb at denali writes:
>
>Some of my comparisons on SCSI, ESDI, and SMDE are below on our product.
>These are on read performance through the EFS.
>
>SCSI:  450 KBS (async, single ended, 10 MHz drive)
>ESDI:  980 KBS (with above features, 10 MHz drive)
>ESDI: 1500 KBS (with above features, 15 MHz drive)
>SMDE: 2100 KBS (with above features, 24 MHz drive)
>

I have run tests using CDC Sabre disks (24 Mhz) with imbedded SCSI
controllers and I got the following results.  These are based on
transfer size of 8192 bytes and synchronous transfer and all accesses
via a file system.

1 disk	444 KBPS
2 disks 795 KBPS 
3 disks 977 KBPS
4 disks 1.102 MBPS
5 disks 1.180 MBPS
6 disks 1.251 MBPS

I ran the same tests on CDC Wren V disks and got similar results, even
though the transfer rate on the Wren is slower (between 12 and 16 Mhz,
depending on the cylinder zone).

>these numbers actually look better on an AIM benchmark, but this BM tends
>to provide varibale results that skew upward in many cases.  As one would
>expect, the file system tends to slow things a bit, and of course multiple
>drives would up the throughput considerably in all cases.  
>

What were the conditions of your tests, such as transfer size, types
of access.  I am not aware of any standard benchmarks for disk
performance.  Sure would be nice to have a level standard of
comparison.



Terry Kelleher, Encore Computer
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