On Wed, 5 Apr 2000, Paul Barton-Davis wrote:
>I've tried a variety of methods to measure the i/o performance I can
>get from 2 of my Ultra2 SCSI disks (Seagate Cheetah and a Quantum
>Viking II). I am hard pressed to get better than 17MB/sec from the
>Cheetah, and 10MB/sec from the Viking.
...
>I am aware that expecting the "80MB/sec" rate is not realistic, but
>these values seem absurdly low. I am trying to figure out why this
Compared to what? The vaporware drives from IBM, Seagate, and Maxtor?
See also:
http://www.seagate.com:80/support/disc/specs/scsi/st34502lw.html
"INTERNAL TRANSFER RATE (mbits/sec)________152 to 231"
That is the "linear velocity" of bits moving under the R/W heads. 17MB/s
is not bad for a two year old drive. There are modern drives with transfer
speeds over 350mbits/sec. One of my IBM drives (one of the newer 18G models)
moves data @ 19MB/s (it's attached to a 2940UW.)
>Adaptec AIC7xxx driver version: 5.2.0/3.2.4
>Compile Options:
> TCQ Enabled By Default : Disabled
...
> Ultra Enable Flags: 0x0000
> Tag Queue Enable Flags: 0x0000
>Ordered Queue Tag Flags: 0x0000
...
> Actual queue depth per device for aic7xxx host instance 0:
> {1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1}
Taged commands are off, there's a speed killer.
> 10: 1740 1756 IO-APIC-level aic7xxx, RME Digi9652
And you're sharing an interrupt. That'll burn a little speed.
>(scsi0:0:0:0)
> Device using Wide/Sync transfers at 80.0 MByte/sec, offset 15
>(scsi0:0:1:0)
> Device using Narrow/Sync transfers at 5.0 MByte/sec, offset 15
...
Umm, I don't think so... 80MB/s is an LVD speed. You cannot have both LVD
and non-LVD hardware on the same cable in LVD mode. There doesn't appear to
be any isolation chip on that MB (and SuperMicro doesn't list one) so it's
actually _40_MB/s but that doesn't matter for the purposes here -- the bus
is faster than the drive. Besides, you've got too many devices to fit on a
proper SE FAST-40 (U2/SE) bus. Again, this is immaterial to speed.
--Ricky
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