Path: utzoo!utgpu!news-server.csri.toronto.edu!bonnie.concordia.ca!uunet!lll-winken!iggy.GW.Vitalink.COM!widener!dsinc!bagate!cbmvax!jesup From: jesup@cbmvax.commodore.com (Randell Jesup) Newsgroups: comp.sys.amiga.hardware Subject: Re: Seagate Drives Message-ID: <21917@cbmvax.commodore.com> Date: 25 May 91 02:19:41 GMT References: <9105152355.AA05412@thunder.LakeheadU.Ca> <42421@cup.portal.com> <21748@cbmvax.commodore.com> <42601@cup.portal.com> <21894@cbmvax.commodore.com> Reply-To: jesup@cbmvax.commodore.com (Randell Jesup) Organization: Commodore, West Chester, PA Lines: 59 In article <21894@cbmvax.commodore.com> daveh@cbmvax.commodore.com (Dave Haynie) writes: >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). SCSI 2 doesn't really mean much. The "good stuff" in SCSI 2 is mainly the 10MB/s "Fast" synchronous mode. For a host adapter, SCSI 2 often merely means that you don't use any non-SCSI-1 commands that aren't in SCSI-2. (i.e. you use don't use anything "funny", and may use one or two new SCSI-2 commands on rare occasion.) We could probably call the 590/2091/3000 scsi a SCSI-2 controller by that definition, though we don't. SCSI-2 can also mean that it's a SCSI-1 controller with a SCSI-2 connector. BTW, 1.8 asynch, 3.0 synch is NOT fast for a modern SCSI controller. Really old ones do 1.5/NA, old ones do 3.0/5.0, and current ones do 5.0/5.0+, and SCSI-2 ones do ~5.0/10.0. (Taken from the NCR scsi chip family - the WD 33c93a chip is around 3-4.0/4.0 I think, the 33c93b is 4.0/10.0.) >>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. 28MB/s includes clock bits, etc, etc. My 400+MB, 4400rpm 3.5" Seagate does 2MB/s sustained on a 3000 through the FS on the outer tracks, 1.5MB/s on the inner tracks. (Note that on the Amiga, max filesystem rates are essentially device rates.) It's a SCSI-2 drive (will do 10MB/s), but that's close to useless to me, since its sustained rate is 2MB/s max. The main putpose of the high xfer rate is for when the drive already has the sector you need in cache, and so you can run more drives on the same bus at their sustained rates. It's absolute max average is 2.1 MB/s at the interface. We've run one of these under Diskspeed at 90+% of maximum speed while running a Quantum 210S at 90+% of its maximum, at the same time (total xfer rate: ~2.8 MB/s) on an A3000. >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. They also get speed with more sectors/track and zone recording (at least on the outer tracks). Apparently they get up to 64 sectors/track. -- Randell Jesup, Jack-of-quite-a-few-trades, Commodore Engineering. {uunet|rutgers}!cbmvax!jesup, jesup@cbmvax.cbm.commodore.com BIX: rjesup Disclaimer: Nothing I say is anything other than my personal opinion. "No matter where you go, there you are." - Buckaroo Banzai