Charles:
Your "old" SCSI is U2W (LVD), may of 80MB/second. Your "New"
SCSI is U160, max of 160MB/second. The difference you're seeing is
because they are different versions of the SCSI protocol, with
differing performance characteristics. For reference, SCSI 1
was 10/MBPS, SCSI 2 was 20/MBPS, SCSI2/Wide was 40/MBPS, etc.
In other words, SCSI is not SCSI! There are significant differences
in the different levels of SCSI implementation
-Scott
Charles Galpin wrote:
>
> Very interesting. This thread prompted me to test the buffered disk reads
> on some of my machines. As expected, my pokey (but trusty) ide drive
> system was slower than the scsi ones. But, what really surprised me was
> the difference in beformance between my two scsi systems - one brnad new,
> and the other not much more than a year old.
>
> "old" scsi setup:
> adaptec 2940U2W
> 2 x 9GB IBM (?deskstar? DDRS-39130D) LVD drives
> I'm pretty sure I have the bios set at 80MB/sec (verified w/ /proc/scsi/*)
> Timing buffered disk reads: 12.85 MB/sec both disks
>
> new scsi system:
> adaptec 29160
> 1 x 18gb seagate ultra 160 (ST318436LW)
> bios set for 160MB/sec tranfers
> Timing buffered disk reads: 25.20 MB/sec
>
> The new system is *twice* as fast. buffer-cache reads are more comparable
> though (but still better on the new).
>
> Now, it's been a long time since I've mucked with the "old" setup so I
> don't remeber if the bios transfer rate can be set above 80 (I don't think
> so), but I'm not getting anywhere near 80 anyway.
>
> I had expected the "old" setup to perfrom as well, or even outperform the
> nw one. maybe I'm just showing my ignorance here?
>
> Does thsi look right? if not, how can I increase performance on the
> "old" setup?
>
> tia
> charles
>
> On Thu, 2 Nov 2000, Ronald W. Heiby wrote:
> > Thursday, November 02, 2000, 2:21:36 PM, Jamin wrote:
> > > As for your performance, you might want to check your HD settings with
> > > "/sbin/hdparm". Unless you are using SCSI drives, you most likely don't
> > > have the drives running with DMA enabled. This roughly doubled my
> > > transfer rates.
> >
> > Wow, what a great suggestion! I ran the hdparm test on my drive and
> > got about 3 Megabytes per second. Then, I turned on DMA for the drive
> > and am getting about 11 with the same test! Subjectively, the system
> > seems a lot "snappier", too.
>
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