--- In firebird-support@yahoogroups.com, Elmar Haneke <elmar@...> wrote:

>
> > Solution:
> > My current solution is to "freeze" or "quiece" the IO to the databse
> > file by setting the database in backup mode. Then to flush the file
> > system buffers to disk using sync.exe and then create the snapshot on
> > the storagesystem. Afterwards the databse backup mode is turned off.
> > ...
>
> In this scenario the database peridoically is offline for an significant
> time. This seems to be an contradiction to the backup-requirement.
>
> Using firebird's backup facilities should be preferrable.

When the databse is in backup mode it is still online. The changes are simply written to the delta files instead of into the database directly. I've scripted the above scenario and it is executed within 30 seconds. I still haven't tested the performance impact when the database is in backup mode and how long it takes to commit the transaction from the delt file into the database, but hope that it's acceptable.
In comparison a backup from the database (26GB) takes 2 hours (not under load).
In case of a crash or logical erro the database has to be available within an hour. This is not possible using a backup restore.

>
> > For how long can the system be unavailable after a failure? You can
> > probably backup a 3GB database in 10 minutes (online, without any
> > "freeze" or "quiesce"), but a restore might take 30 minutes. Maybe
> > this is too much, in particular if your database is large/huge. At
> > least, there is no interruption of service unless a failure happens.
>
> If restore-time is the problem you can restore the Backup immediately to
> an Backup-Database which can be activated in case of an failiure without
> further delay.
>
> Elmar
>