--- In firebird-support@yahoogroups.com, "Leyne, Sean" <Sean@...> wrote:

>
> Mark,
>
> > > In Firebird 2.5 there is config paramter to control this but it's
> > still
> > > RC.
> > > In 2.1 I can either:
> > > 1. switch to classic
> > > 2. disable filesystemcache
> > > What are the experiences with disabling filesystemcache, pros and
> > cons?
> >
> > Why is that a problem? Windows will release parts of the filesystem
> > cache if other processes require more memory. As long as there is no
> > memory requirement, Windows will aim to allocate the remaining memory
> > as cache.
> >
> > In my opinion that is not a burden, and you should not be overly
> > concerned with it.
>
> Have used a 64bit Windows server?
>
> I can tell you from my own experience that when the database or a table (and it's indexes) is much larger than the available RAM, the server will promote too much memory "thrashing", which will results in poor server performance.
>
> Limiting the OS file cache allows the thrashing to be minimized.
>
>
> Sean
>

True.
Here is doomsday scenario.
You have 10 gigs database on reasonably loaded server, and 4 gigs or RAM.
Your FBServer porcess uses around 100MB of RAM
You start manual sweep.
Filesystem Cache uses all available RAM to cache database file (becose 64 bit os does not have limit on ram used for caching).
OS starts using swap instead of RAM
You get bluescreen crash.

So you have to disable filesystem caching on 2.1 firebird that runs on 64 windows server, or use sysinternals to limit ram used for file caching.