Usenet 1994 January/usenetsourcesnewsgroupsinfomagicjanuary1994.iso/sources/std_unix/volume.20/text0007.txt

Internet Message Format | 1990-08-02 | 1.6 KB

From: uunet!Wichita.NCR.COM!Alden.Wilner
From:  [e-mail]

I am interested in finding out the current state of standards efforts
in regards to tape drivers, specifically:

Is there any standard ioctl interface to take advantage of the flexibility
afforded by the SCSI interface?

I have heard rumors that AT&T has come up with a proposal (or perhaps a
de-facto standard in SVR4), but don't have any details.  Can anyone
supply me with some?

Is there any standard action for what a tape driver should do with
internal flags (End-Of-Media, Filemark, etc.) when it receives an ioctl
call (like, clear the "DataWritten" flag so filemark writing won't be
performed after an ioctl)?

Is there any standard defined for what drivers should do with the
bp->b_blkno?  Early AT&T drivers (the Kennedy tape drive?) would
support block device IO to tapes, and would space the requested number
of 512-byte blocks if the b_blkno didn't match the driver's idea of
where it was.  So what happens with, say, 5K blocks on a 1/2" tape
reel?  Or should the driver just ignore the bp->b_blkno field
altogether?

These questions are prompted by the infamous exabyte tape drive.  Since
that thing's so huge, it would be nice to have a way to space around on
the tape so you can write multiple disk backups to a single tape (as,
for example, the Willow tape backup system does).  And it would be
really nice if this method were standardized, either at the ioctl level
or at a library which would translate standard function calls to
whatever the driver prefers for ioctl.

Standard ioctl - what a concept.

Thanks,
[e-mail]

Volume-Number: Volume 20, Number 8