Re: SCSI Harddrive and GS/OS

[dempson@atlantis.actrix.gen.nz (David Empson)]

In article <DEvF17.6wC@actrix.gen.nz>,
David Empson <dempson@atlantis.actrix.gen.nz> wrote:
> 
> Speaking of SCSI hard drives, my [Quantum] Trailblazer 850 has just
> arrived, and I'm in the process of putting it together to test it.

I've now done some testing, and this drive works perfectly on an
original Apple SCSI card and with an Apple High-Speed SCSI card.

I used Chinook SCSI Utilities to partition it on the original SCSI
card, then repartitioned it using Advanced Disk Utilities (once on
each card).

I was able to confirm my previous theories about limits to the number
of partitions.  They are as follows:

- The original Apple SCSI card only supports seven partitions in total
  (over all drives) under ProDOS-8.  With ProDOS-8 1.2 through 1.9, only
  four partitions are available if the card is installed in slot 5, or
  two if it installed in any other slot.  ProDOS-8 2.0 and later can
  remap additional partitions into unused slots.

- The Apple High-Speed SCSI card supports at least eleven partitions under
  ProDOS-8 2.0 or later (if you have enough unused slots).  I wasn't
  able to free up one slot without removing a card, so I didn't try
  twelve or thirteen partitions.  I expect it would have worked.

  According to the technical reference for the card, it supports 111
  partitions via the SmartPort interface.

- Under GS/OS, I was able to access fourteen partitions on the drive
  (ten ProDOS, four HFS) with both SCSI cards.  With my older hard
  drive connected as well, I had nineteen partitions online (the Finder
  desktop was _very_ cluttered :-)).

- The HDSCPARTITION software provided with the original Apple SCSI card
  is only able to create one or two partitions.

- The HDSCPARTITION software provided with the Apple High-Speed SCSI card
  can create up to four partitions.  This version of the program does not
  work with the original SCSI card.

- Chinook SCSI Utilities can create up to seven partitions with either
  card, limited to 32767.5 KB per partition.  It can display
  information about the first nine partitions.

  CSU had trouble displaying some of the statistics for this drive.  I
  expect the numbers were too big for its number printing subroutine - I
  got a question mark for the initial digit of the disk size.

- Advanced Disk Utility can create more than eight partitions on large
  drives, but it sometimes limits you to eight for no apparent reason.
  In one case, I was only able to create more than eight partitions by
  deleting all the partitions except one, partitioning the drive, then
  going back into the partitioning function and then adding them back
  again.

  According to the System 6.0 user manual, Advanced Disk Utility limits
  the number of partitions according to the size of the disk, as follows:

  256 MB or smaller  8 partitions
  320 MB            10 partitions
  512 MB            16 partitions
  640 MB            20 partitions
  800 MB            25 partitions
  1 GB or larger    32 partitions

  It isn't clear what the rule is for drives between these sizes.  I
  expect that ADU divides the disk size by 32 megabytes, e.g. a 384 MB
  drive would be able to have 12 partitions.

> A possibly useful piece of information about this drive: it supplies
> termination power, so I will not have any problems with my SCSI busses
> (he says hopefully).

And I didn't - everything worked beautifully.  This was the only drive
connected to the original SCSI card, and is connected after my old
Quantum LPS240 on my High-Speed SCSI card.


A little information about the drive mechanism:

It is called a "TrailBlazer 850", and has a capacity of about 850
million bytes (Quantum uses the term "megabyte" to mean one million
bytes, not a real megabyte, which is 1048576 bytes).  The actual
capacity is about 830 MB.

The average seek time is 14 ms.  It has a 128 KB buffer.

Further information about the specifications are available from
http://www.quantum.com, along with information about other Quantum
models.


Doing some benchmark tests with Chinook SCSI Utilities, I get similar
readings for both drives: a transfer rate of 614400 bytes per second
using multi-block reading with DMA (12K reads).  The new drive is
slightly faster when reading data normally in ProDOS-8.

The seek time of the new drive is significantly faster than the old
drive (1.3 seconds for 100 seeks across a third of the disk, compared
to 2.4 seconds for the old drive).
-- 
David Empson
dempson@actrix.gen.nz
Snail mail: P.O. Box 27-103, Wellington, New Zealand