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Peter Much wrote:
> So now, if some of You are wondering what I'm actually trying to
> do with Bacula Storage Solution - well I would say I try to
> implement a straightforward ideal storage solution:
>
> 1. backups shall be saved to disk storage
> 2. disk storage shall be moved to tape after a certain time
> 3. tape storage shall be duplicated/mirrored
>
> Concerning 1:
> There are a lot of good reasons to save to disk.
> - You do not need to change tapes
> - The schedules will not interrupt unexpectedly for tapechange
> - Restore does not need a tape to load and works much quicker
> - You can increase backup frequency greatly, you could restore
> an accidentally deleted file even if it was created only
> half an hour earlier
> - You can tune the volume size to your demands
> Concerning 2:
> There are no good reasons to keep older backups on disk.
> - They are seldom required
> - They occupy a *lot* of space, which can find better use
>
> There are some more good reasons for 1+2:
> - I am seldom and irregularly on-site. Nevertheless I want a
> regularly scheduled backup - because when it is "manually
> initiated backup", then it quickly becomes "no backup at all".
> So the backup should go to disk, and when I'm on-site, I can
> manually start the migrate-to-tape (which I MUST do because
> otherwise the disk fills up).
> - The tapedrives can be powered off. They are noisy, and they
> add to the CO2 production.
> - disk-buffering is implicite, so no "shoe-shining".
>
> Concerning 3:
> A tape cartridge is no more reliable than a disk.
> Actually you SHOULD be able to restore most of the data even if
> a piece of the tape is damaged, but with any modern tapedrive
> I think if the header of the tape cannot be read in an orderly
> fashion, then it gets similarly difficult as restoring from a
> broken disk, i.e. it needs special facilities.
>
> Now with disks it is totally convenient to have mirroring. Actually
> I can choose for every filesystem if I want to take the space from
> mirrored storage or from simple storage.
>
> For tapes there is obviousely no way of *mirroring*, as they are
> streaming devices. So there should be a way of duplicating,
> if in realtime with two drives or sequentially with one does not
> matter much, but with a finer granularity than image-copying
> whole tapes, and someway managed by software, as it is really
> boring to do this manually.
>
>
> Now putting this into practice with Bacula gives a couple of issues,
> which I am currently working on.
Your writeup is very well done. I would ask that when you DO figure out
how to do this , you share some of your documentation as it somewhat
looks like you will be writing some and that it would be something that
would be helpful to have in the wiki.
To the technical points you discuss, you will discover that tape
mirroring is a problem, as currently choosing which media from which to
restore is not something that would work with Bacula the way things are
now. You can run two backups, but for some places this is not compliant
with policy, as the backups will by definition NOT be identical.
- --
---- _ _ _ _ ___ _ _ _
|Y#| | | |\/| | \ |\ | | |Ryan Novosielski - Systems Programmer II
|$&| |__| | | |__/ | \| _| |[EMAIL PROTECTED] - 973/972.0922 (2-0922)
\__/ Univ. of Med. and Dent.|IST/AST - NJMS Medical Science Bldg - C630
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