Kjell Rilbe wrote:

> Do you mean that some file systems (on Linux?) have a write cache but
> ensure that writes are performed in the order they are queued?

Yes, something like that.

> In either case, I assume the disk still has to perform the same sequence
> of seeks and writes to do its job, so with a constant commit rate the
> performance will be the same as without this kind of cache. Same
> "motorcycle effect". Right?

Performance is nearly the same, but consistency is much higher. If you
have a filesystem with ordered writes, metadata (directory structure,
which bytes go into which file, etc.) is kept in place and data is
written in such way that Firebird easily detects unwritten stuff as
uncommitted transactions. Without ordered writes you can easily end up
with part of some other file in Firebird database file after a power
failure (for example, if database file grows and needs to grow the file
on disk). Having a part of some other file in FB database is corruption.


--
Milan Babuskov
http://www.flamerobin.org
http://www.guacosoft.com