[Info-vax] strange backup behavior

[AEF]

On Aug 10, 11:48 am, B Hobbs <bdhobb... at acm.org> wrote:
> On Aug 8, 9:42 am, AEF <spamsink2... at yahoo.com> wrote:
>
>
>
> > On Aug 8, 9:07 am, sapienzaf <sapie... at noesys.com> wrote:
> > > On Aug 7, 11:55 pm, David J Dachtera <djesys... at spam.comcast.net>
> > > wrote:
>
> > > > The OP may be looking for info relating to "fast skip".
>
> > > I'm sure this is an emulation problem.
>
> > > He's running Charon-VAX which makes OpenVMS think the SDLT tape drive
> > > is a TK50.  I don't believe fast skip is an option for a TK50, and
> > > furthermore he's running VAX/VMS v7.1 which (IIRC) does not have the
> > > $SET MAGTAPE/FAST_SKIP command.
>
> > But the tape must be being rewound between each BACKUP save operation.
> > It appears that /VERIFY is not present. Perhaps he is MOUNT-ing and re-
> > MOUNT-ing between each BACKUP operation? We need to see his command
> > procedure.
>
> In the procedure, allocate the tape drive, mount/foreign the tape,
> position to the end, loop thru the backups, dismount/nounload the
> tape, mount, directory of the files, dismount/nounload, deallocat,
> exit procedure.  No, the tape is not mounted and dismounted between
> backup steps.  There are only two pairs of mount and dismount, one
> pair as /foreign for the backups, one pair without /foreign for the
> directory list.
>
> The backup procedure is 36 blocks, I'll post the complete procedure if
> requested.  The log files range between 300 and 35,000 blocks, I think
> I'll be butchering those as needed.

The .com file would be helpful.

> I only *suspect* the tape is rewinding between backup commands, but I
> can't think of anyway to confirm this except the amount of time the
> marker files take to backup.  Tell me again why cartridge tapes are so
> much better than nine-track tapes where one can actually observe the
> tape rewinding between backup steps?  :-(

I don't see how it couldn't be rewinding for each save set. Maybe
there's a bug in BACKUP or your tape drive or controller.

Are you perhaps running $ set magtape/log/skip=end_of_tape mua0:
between each backup? You don't need to do that, though I don't know if
this might be causing your problem.

> > To the OP: Why are you not using /IMAGE instead of /FAST [000000...]?
> > Why are you making both a journal file and listing file of each save
> > set?

Come to think of it, I don't think /FAST buys you anything for full
backups. It's really useful  as follows:

A fast file scan is most useful when the input specifier includes most
of the files on the volume, and file-selection qualifiers (such as
those that pertain to date or owner) specify a relatively small set of
the files named. Because image operations implicitly use the fast file
scan, the /FAST qualifier is ignored if used with the command
qualifier /IMAGE.

>
> The procedure loops thru the disks, executing pretty much the same
> backup command on each disk.  There is an embedded symbol in the
> backup command that shows up as an empty continuation line for most of
> the disks, for some disks this symbol contains an /exclude.  /Image
> ignores /exclude, it was simpler to use the same command for all
> disks.  It wouldn't be difficult to change to /image for some disks,
> but I didn't see much advantage from reading the documentation.

BACKUP/IMAGE preserves volume characteristics (everything you specify
with the INIT command, and subsequent SET VOLUME commands). It also
preserves aliases. Lost files and files marked for deletion are also
saved. It also provides a functionally equivalent copy. This is not
necessarily the case with non-image backups.

I would also guess that restore operations from /image backups would
go faster as directories don't need to be updated for each file
restored.

You can set the files to exclude as "backups disabled" using SET FILE/
NOBACKUP depending on the nature of the files. This is done by default
for page, swap, and system dump files on the system disk, as data in
them is useless after a crash or shutdown. If this is not the case for
these files, then why aren't you backup them up? I'm just asking.
Perhaps they're easier to regenerate than to restore from tape.

Why to you use /LOG, /JOURNAL, and /LIST? Isn't that rather redundant?

>
> I apologize for not answering sooner, I had weekend Reserve duty and
> was busy making the planet a safer place for VMS geeks
> everywhere.  ;-)

Thanks!

AEF