> gfix -write async test.fdb -user sysdba -password
It, of course, has a tremendous impact on such tests.
Though, everybody should carefully consider wether the
risks of data corruption are acceptable (or not) using
sync writes off. I know most people here do know, but I
wouldn't like you to get mislead by this recent topic.
There are a large number of past discussions in this list
archive about this very topic. May I recommend reading
them even if not all do apply as severely to recent
Firebird versions as older Interbase(R) editions.
At the very least, to make it short, Firebird uses an
ordered-writes technique to help preserve its on-disk
structure in case of unexpected interruption. As soon as
the OS is allowed to delay writes as it sees fit, that
integrity security is lost. And the OS can go quite far in
not following the initial order of the writes: plain-old
common scatter-gather techniques can optimize the writes
in such an unwanted way. So it is not just a matter of how
much data may be lost by loosing computing resources right
in the middle of some transactions, but how far the whole
data is still meaningful after such an event, knowing that
the ACID rules might have been broken by the OS
re-ordering individual writes which did belong to various
Careful backup plans or more advanced storage
architectures (async DB on synced volumes exposed from
heavily caching SAN subsystems, for instance) are required
to overcome the risks of integrity loss. The path to
follow depends on the amount of unavailability of data
(during restoration) or data loss which is acceptable, and
of course the amount of money available for
On simple setups, using FB sync writes on SSD might be
decent tradeoff between integrity assurance and speed.