Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!think.com!zaphod.mps.ohio-state.edu!mips!atha!aunro!ukma!rutgers!cbmvax!daveh From: daveh@cbmvax.commodore.com (Dave Haynie) Newsgroups: comp.sys.amiga.hardware Subject: Re: Seagate Drives Message-ID: <21748@cbmvax.commodore.com> Date: 20 May 91 18:30:33 GMT References: <9105152355.AA05412@thunder.LakeheadU.Ca> <42421@cup.portal.com> Reply-To: daveh@cbmvax.commodore.com (Dave Haynie) Organization: Commodore, West Chester, PA Lines: 63 In article <42421@cup.portal.com> FelineGrace@cup.portal.com (Dana B Bourgeois) writes: >On a related note: >Seagate tells me they will be announcing/shipping a new (very large) >drive this fall. It is about 2.4 Gbyte unformatted. >OK, finally for my questions: > 1. What is the fastest sustained throughput drive the Amiga > can handle? 20 MHz? 28MHz? What if any 'magic' is needed > to handle such a drive? Controller/memory/etc. Specifying a frequency here is meaningless, because you're interested in bandwith. Bandwith is generally measured in bytes/second, which gives you numbers that are independent of system architecture. All things being equal, a system that manages 10MB/s could be a 64 bit RISC thing clocked at 1.25MHz, a 68000 clocked at around 20MHz. Anyway, in the A3000, the weakest link is the SCSI bus. It runs somewhere about 5MB/s in synchronous mode, which the A3000 SCSI hardware has no trouble keeping up with. Actual transfers from the DMA controller's FIFO to memory happen at around 20MB/s. > 2. Sun and other workstation vendors already claim to use > SCSI 2. Does CBM have plans to support it? I'm not asking > about products. More design philosophy. Will SCSI 2 give > enough increase in speed to make a viable product as opposed > to a 'me-too' marketing product. There is a SCSI-2 version of the A3000's Western Digital SCSI chip. Right now, they don't have a scsi.device for it. It's probably not going to buy you much anyway, though, since even with killer drives, you're going to be limited by the speed of the drive. The main advantage of the faster modes on SCSI buses is when you have multiple drives in place. > 3. I see transfer rates being batted around in workstation/unix > magazines of 4-5 MB/sec. Nearly all of the system benchmarks I've seen (in places like "UNIX Review" and "Personal Workstation") measure disk rate in KB/s. Most UNIX systems can sustain 350-500kB/s. A few really good ones go higher, but not many. At least until you get into RAID boxes instead of single SCSI drives. For example, the April 1991 issue of "UNIX Review" tests a few low cost UNIX systems. They get a maximum of 617kB/s for the Sun SLC, 436kB/s for the DECstation 2100, 295kB/s for the HP DN2500, and 423kB/s for a generic '486 PClone (all sequential reads, see page 49 for more details). > Used to be people on this thread said the Amiga's 1.2 MB/s SCSI was > one of the fastest SCSI implementations going. I've seen Amiga > numbers around 2 MB/s. Have SCSI designs on other machines really > tripled/quadrupled in speed? For the most part, no. You're either looking at the wrong numbers, or thinking of some pretty expensive workstations. Also, beware what you're looking at. Drive people like to talk in terms of peak transfer rates, rarely sustained transfer rates. Real meaningful benchmarks have to reflect what's happening through a machine's filesystem, which is what you're seeing with Amigas in most cases. The filesystem takes into account Disk, SCSI, host adaptor, device driver, and filesystem efficiencies. >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.