Re: [SLUG] Backup rotation schemes

[Jon Biddell <jon@xxxxxxxxx>]

At 01:03 15/09/01 +1000, Minh Van Le wrote:
> Are there other rotation schemes other than GFS & Tower of Hanoi ? which
> seem to be most popular.
>
> I don't think many people prefer Round Robin.

We (at work) use a 4 week cycle - like this;

Monday - Thursday week 1 are differential backups.  Friday is a FULL backup.
Same for weeks 2, 3 and 4.

Then a FULL backup on the last business day, like this;

If the month finishes on a Friday, Saturday or Sunday, the full backup is 
Friday night.
If the month finishes in the middle of the week, then the full backup is 
the first FRIDAY of the following month.

Monthly backups are archived permenantly, weekly tapes re-cycle every 4 weeks.

The advantage doing a differential, rather than incremental, is that a file 
modified on Monday is also backed up on Tuesday, Wednesday and Thursday. 
With an INCREMENTAL, the Monday file will only be on the Monday tape, as 
the archive bit is reset after backup.

After the FRIDAY backups, all archive bits are reset.

With our network of (too bloody many) Evilware-NT servers, this uses 4 DLT 
tapes each night, and a set of 4 for the MoNTHLY, making a total of 80 
tapes in the rotation pool at any one time - at $115 a tape, it ain't cheap.

Although we have just taken delivery of an IBM LTO drive with 7 tape 
autoloader, hiving us 1.4 TERABYTES of backup - down to 1 dape a night and 
maybe 2 for Friiday and Monthly (although we haven't used more than one yet 
!!!).

Jon