SUMMARY: New SCSI/Eth Sun cards *really* faster ?

From: Claude Scarpelli (
Date: Fri Oct 23 1992 - 20:22:06 CDT

In a previous message, I asked sun manager list about the effect of new
SBus SCSI card on disk performance (see that message at the end).

Most of the answers says that disks have limited "head-to-platter"
transfer rate. This limit depends (at least) on the disk rotation

More, the disk should support fast SCSI controller. In the SCSI chain,
if you mix 5Mb/s and 10Mb/s disks, everybody will work at 5Mb/s.

In summary, you can take advantage of 10Mb/s SCSI card if :

1) All yours disks have 10Mb/s interface, and high transfer rate
   (rotational speed).

2) You have disks with 10Mb/s interface and *low* transfer rate. In
   this case, you may see better performance when accessing two or more
   drives at the same time.

Thank's to everybody who answer (more than 40 answers).
Claude Scarpelli Internet :
Human Polymorphism Study Center or :

Included messages :

I have just received the new Sun SCSI/Eth card, ref X1053A. This is a
card which is usable on all SBus machines (IPX, SS2, SS10, 6xxMP). The
Ethernet interface is TP. The SCSI interface should run at 10Mb/s (2 times
faster than older).

I have put this card in a SS2 with SunOS 4.1.3 and see no differerence
with Sun 1.3Gb disks. I have done the following test :

time dd if=rsd5c of=/dev/null bs=512k count=200 time dd if=rsd5c
of=/dev/null bs=16k count=10000

The first command performs reads of big blocks, while the second on
performs reads of small blocks. Doing that, I only access the most
externals tracks of the disks. I agree this is not a good test : This
is not the current problem.

With 1.3Gb Sun disks connected to the built-in SCSI interface of the
SS2, user time for the first command is 32s. For the second, it is 66s.
I can't figure out why there is no difference when I connect the disks
on the new SCSI interface.

First test give a *throughput* of about 3 Mb/s with the built-in
interface. With a 10Mb/s interface, I would expect 1.5 to 2 times

Did I miss something ? Is these new card usable at full speed on new
SS10 only ?

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