On 2018-01-26 00:44, Clem Cole wrote:
On Thu, Jan 25, 2018 at 4:57 PM, Mark Pizzolato <m...@infocomm.com
<mailto:m...@infocomm.com>> wrote:
I think the documentation comment “cannot write variable-length
blocks and do not allow skipping forward over records between read
operations” was written when talking about the common cartridge
tapes that were available on 80s and 90s Unix workstations. I don’t
recall the name.
That was not UNIX, that was the QIC standard. Yes, those were blocked
at 512 bytes. Apollo's domain systems had a b*tch of time with them
because their standard disk block was 1056 bytes
Hmm. Ah. THose QIC tapes. Never liked them much, and never played much
with them.
Domain OS using 1056 bytes? On what systems? I used a lot of DN3000,
4000 and 5000 systems, and they used bog standard disk drives with 512
byte sectors. (Interesting systems in some ways, but their windowing
system was pretty horrible.)
These things only supported fixed block size operations and not
variable record lengths (i.e. 80 byte tape labels, then different
sized data records, etc.).
Right the 80 byte ANSI label, then different length data records. UNIX
handles that fine, even with RMT. FYI: My grad school housemate, Tom
Quarles (of SPICE3 fame) wrote the ANSI tape and bunch of
other tape support that most UNIX systems used, explicitly so he could
read/write VMS tapes for the DEC guys who were doing some of the funding
of the USB CAD lab. Leffler (who wrote rmt) used Tom's tape stuff for
the original debug of rmt.
Given that the remote tape drive was a drive which could do
variable length record activities, I think MultiNet’s rmt support
actually worked well. I don’t remember testing it though. Whether
someone should try to do that now to backup simulated VMS systems is
another subject I may write about a little later.
Understood. I was just suggesting trying to keep another emulated
system out of the scheme and going directly to the remote device either
through DECnet or rmt or maybe even using a NAS as virtual tape files.
It just seemed running a Linux with a tape and then running an emulated
VAX on top of that seemed like an extra layer of indirection if there
was an easier path.
Yes, I think the approaches are trying to do things in too complicated
ways as well.
Johnny
--
Johnny Billquist || "I'm on a bus
|| on a psychedelic trip
email: b...@softjar.se || Reading murder books
pdp is alive! || tryin' to stay hip" - B. Idol
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