Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!usc!cs.utexas.edu!sun-barr!rutgers!cbmvax!daveh
From: daveh@cbmvax.commodore.com (Dave Haynie)
Newsgroups: comp.sys.amiga.hardware
Subject: Re: Seagate Drives
Message-ID: <21894@cbmvax.commodore.com>
Date: 24 May 91 17:03:24 GMT
References: <9105152355.AA05412@thunder.LakeheadU.Ca> <42421@cup.portal.com> <21748@cbmvax.commodore.com> <42601@cup.portal.com>
Reply-To: daveh@cbmvax.commodore.com (Dave Haynie)
Organization: Commodore, West Chester, PA
Lines: 45

In article <42601@cup.portal.com> FelineGrace@cup.portal.com (Dana B Bourgeois) writes:

>First, I am talking about a SPARC 2 so I don't know if that is considered
>a low-cost workstation or not.  You didn't mention it when listing a few
>models so I'd guess not.  SUN prints numbers like 2-3 MB/s for it and
>claims it is SCSI 2.  (oops, they claim 1.8 MB/s, 3 MB/s synchronous).

I haven't seen any numbers for a SparcStation 2.  You have to be a little 
careful about what the vendor of a system says (of course you won't notice that
I'd the "vendor" here), versus what a reviewer actually measures in a review.
Unless they have an asterisk next to the numbers, and you read at the bottom
of the page something like "...as measured with [insert favorite disk speed
measurement tool here]".

>Second, after I posted my qustions I received the latest Seagate catalog.
>They have some 5400 RPM SCSI-2 drives they rate at 28MB/s internal
>transfer and 10MB/s external transfer.  Do you think they are saying
>the drive has the capability to transfer data+clock bits at 28MB/s
>and the SCSI protocol is holding it back to 10?  (I ask Seagate and
>their sales people won't speculate.)

My guess is that they can grab data from their on-drive cache at 28MB/s, and
send it over at the full SCSI-2/8-bit speed of 10MB/s.  I don't believe for a
second they get sustained 28MB/s or 10MB/s from the drive itself.

>If sustained transfer rates are increasing from 500KB/s to 2MB/s then there 
>must be more bits per track since the fastest spinning drives are increasing 
>RPM by only 50%.  

The trick is, the fastest and most expensive drives are also big.  So rather
than a single or a pair of heads as in your lower density Quantums, they may
have 6 or 8 heads, maybe even more (I don't know the typical number these days
on a big drive).  The faster rotation gives them a little better per head
speed and a little less rotational seeking latency, but they really get speed
with more heads.  And the caches that most of them have.  Regardless, I don't
think you're going to get close to saturating SCSI off-peak without multiple
drives, no matter who's making them these days.

>Dana Bourgeois @ cup.portal.com


-- 
Dave Haynie Commodore-Amiga (Amiga 3000) "The Crew That Never Rests"
   {uunet|pyramid|rutgers}!cbmvax!daveh      PLINK: hazy     BIX: hazy
      "That's me in the corner, that's me in the spotlight" -R.E.M.