=> On Tue, 2 May 2000 07:35:43 +0200, sal Salak Juraj <sal AT KEBA.CO DOT AT>
said:
> Allen,
>> There is simply no technical reason to prefer a full/incremental scheme
...
> There is one reason for not to go with incremental backup: the restore
> speed. Due to its very nature, the restore speed will be slower comparing
> to restore from full backups. (when both use same tape HW) Depending on
your
> requirements an environmenmt this limitation does not necessarilly have
to,
> but do can apply.
> best regards
I'm sorry, but I must respectfully disagree with you. In fact, a
well-managed incrementals-forever scheme in a system like ADSM can be faster
than a full/incremental scheme. Consider:
On any day except the day the full was taken, you must mount a minimum of
two
tapes to complete a restore.
A TSM stgpool with colocation active (and adequate media levels) will only
need a single mount, unless there is more than one tape's worth of data.
There are of course variables in either scheme:
If you're using "true incrementals", i.e. only backing up files changed
since
the last _backup_ instead of since the last _full_, you can require a whole
weeks' tapes.
You could have your data on a mostly-reclaimable tape, in which case you
might
need a second mount.
etc. etc. etc.
But in any case, a well-implemented storage managment system will be better
than the average case for a full/incremental scheme, and will be much better
than the worst case.
Allen S. Rout
NERDC TSM admin
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