On Tue, 16 Jul 2002, Jon Biddell wrote:
> Monday night - Incremental - Monday's files
> Tuesday night - Incremental - Monday's files, Tuesday's files
> Wednesday night - Incremental - Monday's files, Tuesday's files'
> Wednesday's files
> Thursday night - Incremental - Monday's files, Tuesday's files,
> Wednesday's files, Thursday's files
> Friday night - FULL BACKUP - all archive bits reset
Wasn't that pretty much what I said in my original reply? With the
exception that I allowed for the possibility of a weekend backup too?
Grandfather-Father-son system - standard recommendation from Veritas,
ArcServe, all the commercial mobs.
> The following week the cycle repeats on tape set #2 - this continues for 4
> weeks, then set 1 is re-cycled (which is after the permenant full backup
> is taken, usually but not always)
This bit is different from the recommendations. The way I learned it {all
those years ago!}, after the first week, the weekly backup is kept {I.E
Friday's tape}, the incrementals are re-used for the next week, and a new
Friday tape is inserted for the next fuul backup.
Second week, same deal. Carry on until 4th week of the "month".
At the end of the month, the _LAST_ full backup is kept as a monthly tape,
and _all_ the other tapes are re-used back where you started from. At the
end of the year, you have a single yearly backup which is, in effect, only
a snapshot of a single day, and is completely inadequate for legal
purposes.
However, this has glaring weaknesses for permanent backup - for example,
take a file that is created on Monday.
It's backed up Monday night, Tuesday night, and Wednesday night, but
deleted on Thursday, so it's not backup up on Thursday night, or in
Friday's full backup.
Once the next week's Thursday comes around, there is absolutely *no*
backup of this file - and if the user comes back two weeks later and wants
it back, they've got bucklies.
> This means that a restore SHOULD require only one tape, or a full and an
> incremental in some circumstances.
And is still open to lost files, vis-a-vis above.
> Of course, a backup server with a removable drive caddy, configured (for
> example) as /dev/hdb, with a few removable drives (one per day) would be
> a faster, but probably more expensive, option than the backup
> server/tape combo...
_Bucketloads_ more expensive - especially if you're talking a really big
RAID array to backup.
> As for software, I've had good results with Arkeia, BRU, and (believe it or
> not) ArcServe for Linux - but I still fall back to good ol' tar or cpio
> for most of the work....
Best way to go, I reckon. All these fancy solutions don't replace adequate
record keeping and sane tape rotation schemes. Especially since Linux is
nice enough to include all these wonderful tape utilities in the
distribution!
DaZZa
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