OT: Tape backup scheduling: was: Unix stutter

[John Esak]

> My take on tape backup is to get it going as fast as possible so it
> is over as soon as possible.  And if you are doing this at night
> are there users on the system then?   There shouldn't be, but if
> there are, can you trust your backups?
>
> Bill

Yes, absolutely there are users at night when the backup is done. We are a
24/7 manufacturing facility with multiple locations... It has been VERY hard
to NOT go down, look for redundancy, never be able to safely reshuffle files
(without lots of preparation), etc. Big hassle, but can I trust my backups??
No, of course not, not really. There are files which have headers and
details separated amongst many files. It is altogether possible I might get
a mismatch just based on that time differential alone, let alone other more
typical problems.... But, I have to do a complete backup every night and
simply have to bite the bullet as to the snapshot at the time being good
enough or close enough should I ever need a massive or even selective
restore. It's a problem. I do a differential during lunch every day... that
helps... and a monthly... which by the way saved our ass the other day...  I
have four tapes left in the juke box and I want to figure out how best to
use them to be able to get back to any day. Let me tell you how my present
system nearly screwed me last week.

To all:

I do the following for backups.

Master backup
every night at 11:45pm,  7 tapes

Differential backup
every day at 12:30pm,    7 tapes

Monthly backup
first day every month at 4:00am,  12 tapes

This leaves 4 tapes of a 30 tape jukebox.

Now, it was the 14th of the month. We had a problem that was created on the
second and third of the month, so we wanted to retrieve the data from around
(actually before) those days. Thank goodness the tape for the month had been
done and we returned the file in question back to its state on the first of
the month. Great, that I had just started this new methodology.

But, what am I going to do when we come upon this situation.  It is the 14th
of the month, and we need to return a file to its state after the 3rd of the
month and before the 8th of the month. Since our nightly only go back a
week... we would be screwed.  How can I run a system that will let me get to
any day of the year?

I remember playing with this a lot a long time ago... and we even published
a pretty good scheme back then which did the grandfather/father/child type
thing... which was something like this:

Nightly backups every night on tapes labeled Sunday through Monday,
Weekly backups every Monday onto tapes labeled 1st wk, 2nd wk, 3rd wk, 4th
wk and 5th wk
Monthly backups onto tapes labeled January through December.
Quarterly backups labeled 1st Qtr., 2nd Qtr. 3rd Qtr, 4th Qtr.
Yearly backup as each year passes for archiving.

This system is/was better, but still doesn't do what I want.  Also, it is
too many tapes for a 30 tape changer... and these jukes are $10k each so
buying more of them is prohibitive, even though I'm quite sure many larger
companies/installations do this for their tape libraries.

Anyway, does the only way to be safe mean making one tape per day?  Other
than that do some more differentials? I even have thought about 15 nightly's
and 15 differentials. Seems better granularity that way... but less monthly
help...  Finally, of course I have thought of 30 tapes, one per day, but
then you get those pesky months with 31 days in them... :-)

Anyway, what are some of the other schemes out there. Do they cover you
absolutely back to any particular day or any particular day within a month?
I realize it is all a matter of how close you want to get to the time of the
backup vs the work day. I guess the daily differential at 12am makes me feel
pretty safe. We are only 4 hours of time (upstairs accounting time that is)
away from any backup. We are 12 hours away from a downstairs production
glitch.  I know nothing is or will be perfect, but how can this be
optimized?

Thanks,

John