> What if you put the 2 Gb RAM in the box, but let Linux use it as a disk cache?
> I'm not sure how the disk caching under Linux works, but if you create a file
> and then delete it before it actually gets written to disk, is there any disk
> activity required?
> Sure, the disks will be thrashing away, trying to keep up, but would the I/O
> actually block if there was still room in the disk cache?
Yes it will block. That's the whole point of the fsync() calls embedded within
qmail. The code wants to be sure that data is on disk before proceeding. The
only caveat is that some file systems may *lie* about the results of their
fsync() and tell the process that the data has been placed on disk when it
still sits in memory. In that sort of scenario you may well gain, especially
if the I/O queue is subsequently sorted by cylinder prior to sending to the
disk.
As others have said, it's the cost of seeking - the amount of data is
often trivial. Thus the concept of zeroseek which is pretty similar to
what a journalling file system is trying to do on a more general level.
Regards.
