bill@bcsfse.UUCP (09/29/87)
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I want to connect a 1/4" cartridge tape drive to my computer, but I have
some questions about doing so. I would appreciate any help you all-seeing
all-knowing guru wizards can provide.
1. Any recommendations on the type of drive to buy? Where to look, who
to contact, how much should I expect to pay?
2. I have a set of tape driver devices built into my system. Is it
reasonable to expect them to work with any tape drive connected by
a SCSI interface? In other words, the interface protocol is standard
but is the device command syntax standard?
3. What problems might I run into if I try to connect more than one
device to the SCSI "port"? I would also like top connect a large hard
disk, but am I only going to be able to have device connected at a time?
4. Any other difficulties anyone has experienced or experiences you would
like to share.
The Machine (if it is relevant)
Megadata 8300-7
68000 Unix box
--
Bill Sears ...!uw-beaver!ssc-vax!voodoo!bcsfse!bill
FSE development project
All I ask of life is a constant and exaggerated sense of my own importance.agnew@trwrc.UUCP (10/02/87)
In article <133@bcsfse.UUCP> bill@bcsfse.UUCP (Bill Sears) writes: > > 2. I have a set of tape driver devices built into my system. Is it > reasonable to expect them to work with any tape drive connected by > a SCSI interface? In other words, the interface protocol is standard > but is the device command syntax standard? > Not even all the SCSI interfaces implement the same subset. There is something called the "command command subset" which some controllers support. However, you've got a bigger problem! SCSI is only a transport layer protocol; you have to make sure that the tape controller supports the appropriate tape "standard" like QIC-24, QIC-32, QIC-02, etc. Make sure your drivers support it. > 3. What problems might I run into if I try to connect more than one > device to the SCSI "port"? I would also like top connect a large hard > disk, but am I only going to be able to have device connected at a time? > To use more than one SCSI device (8 maximum) on the bus, all of the controllers must support the "attention" bit. The biggest problem with a SCSI streaming tape is that many SCSI tape controllers cannot or will not disconnect from the bus during slow operations like tape movement to give the disk a chance to do a few reads or writes. This effectively defeats the so-called "streaming" action. A good example of this is the SUN-2 and SUN-3. Without a large buffer, a SUN-3 can take an hour to search a 1/4" cartridge. To get maximum performance out of multiple disks on the bus, the SCSI disk controllers must disconnect while doing a head seek. Also they should support "multi-threading".