Date: Sat, 25 Oct 2003 07:49:17 -0400 From: jim page <[EMAIL PROTECTED]>
the specs on the disk say it can dish out 20MBs per sec http://www.drives.net/ST39216N.htm
Well, there's the electronic's data transfer rate, and the media's data transfer rate. That page gives you the electronics' (i.e. the SCSI bus's) data transfer rate, which bares nealy no relationship to what the heads and platters of the drive can actually deliver. All the drive manufacturer's do this. A few of them have started including another number which is an estimate of the actual performance. At least, I've seen such a number on a spec sheet once or twice.
All that said, you have another problem. The Jackhammer can handle 20 MB/s in Fast & Wide mode. The 39216N is a narrow (50 pins) drive, which is going to limit you to Fast mode, no Wide. The maximum performance on a Fast Narrow SCSI interface is 10 MB/s.
If you connected the drive to a more modern Ultra SCSI card, then you could (in theory) get 20 MB/s on the narrow interface. But there is no Ultra SCSI card for the NuBus machines, only Fast and Fast & Wide.
got the following timing figures from FWB hard disk toolkit 4.5 - pre jackhammer, using sys board, bus 0, 4.5 MBs per sec - using jackhammer, comes up as bus 2, tests out at 9.1 MBs per sec
heard rumors that nubus limitations would top out at 10MBs per sec
You probably heard that NuBus runs at 10 MHz. The theoretical (using poor theories) maximum transfer rate on NuBus is 10 MHz X 32 bits = 40 MB/s. Because of the time to set up transactions and stuff, you'll never get a rate that high, but with block transfers, you can probably get close (like 80 - 90 %).
Or it could be that someone was pointing out what happens when you put an Ultra SCSI narrow drive on a Fast SCSI bus, which is that it drops back to Fast SCSI and the best you can get is 10 MB/s.
- any way to more than 9MBs per sec out of my current drive, w/o striping, etc
No, because of the bus issues mentioned above.
That may also be as fast as that drive will work. I have some ST32550W drives which also have a 20 MB/s Fast & Wide interface and the best they will do in practice is 6 MB/s. They're older than your 39216N. The platters and heads just can't deliver more than 6 MB/s.
- was wondering if a 68 pin F/W drive can go over 10MBs connected to a jackhammer given the nubus rumors. anyone got one to try out ???
Yes, definitely. Kaye, over at MacGurus had a tricked out 9150 with some super fast modern SCSI drives. I think he had LVD U2W drives on a granite cable in single ended mode connected to the JackHammer. He pushed it close to 20 MB/s, but those drives will deliver 20 MB/s or more with just one by itself.
However, he tried various RAID configurations as well, including putting one drive on each of two separate JackHammers and found that the RAID didn't really improve performance any. Instead of using the RAID'ed drives concurrently, the machine seemed to access them sequentially. He wasn't sure if this was a limitation in teh RAID driver software on NuBus machines, or if it has something to do with NuBus itself or the JackHammer.
Jeff Walther
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