> 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.

> 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