On Friday 09 December 2005 09:20, Ribi Roland wrote:
> Hi,
>
> We need to archive yearly backups 5 years and schould be able to restore
> those tapes.
This *should* be possible providing you have good media, don't change tape
drives, and keep the same tape blocking.
>
> Can I read/restore old tapes, written by old versions of bacula with a new
> Version (1.36 to 1.38)?
Yes
>
> How often are there changes to the format how bacula writes tapes?
The first format was used 2 years, the second has not changed for 3 years now.
Bacula *should* still be able to read the first format.
>
> Which settings of the storage deamon are important to restore old tapes?
The Device resources.
=====
Yes, this is a *very* good and important point. I recently said that Bacula
doesn't maintain backward compatibility, but I wasn't very specific about
that. What I meant was that generally you cannot mix different versions and
have them inter-operate unless the first two numbers of the version (e.g.
1.38 of version 1.38.2) are the same. The third number ( 2 in the example )
can vary and simply means a bug fix of the 1.38 stream.
Concerning reading tapes written by an older version of Bacula: the goal is to
be able to read any tape written by Bacula with a newer version. This is the
*goal*. I think there have been something like 11 versions of the tape
format, most very minor tweaks that would not modify compatibility. There
have been two major formats, the second of which was made in version 1.27 in
November 2002. So, the tape format has been unchanged now for 3 years.
Now, I have never tried to read a pre-1.27 tape recently. Bacula *should* be
able to read them, but who knows ...
I am considering making one more change in the tape format in the near future,
but it too will be backward compatible (there are several version indicators
on the tape). I'm still turning this over in my mind as it is possible to
make the change only in the software (i.e. keep the current format, and
change it on the fly as the data is read/written from the new format to the
old format).
That said, as time goes by, since the tape format well defined but extensible,
we add additional data to it such as ACLs, Win32 data, encrypted data, ...
so, an older version of Bacula might not be able to read all the data that is
written with a newer version.
If you want to be 100% sure that you can read old tapes, there are two
strategies:
1. Try reading old tapes from time to time -- e.g. once a year.
2. Keep statically linked copies of every version of Bacula that you use in
production then if for some reason, we botch up old tape compatibility, you
can always pull out an old copy of Bacula ...
--
Best regards,
Kern
(">
/\
V_V
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