Alan,
I ported the SMP Oracle to NetWare in 1994, and from what I've saw of
their internal architecture (which is like most databases) they always
seem to assume they have a more direct interface to the file systems
(i.e. on NetWare, Oracle uses the DirectFS interface which by-passed the
cache completely). Oracle also provided it's own caching above the OS
for remote SQL users. When they called DirectFS, it was always with an
"O_SYNC" semantic, which I think is the spirit here. If the database is
using fsync() all the time, one would assume it's because they are doing
a commit operation (or updating a rollback segment) and expect a
write-through to occur.
I think this is not as critical as you think for Databases unless
there's some database implementation out there that isn't optimized as
well as Oracle, in which case, it should not be doing O_SYNC calls all
the time, just on commits or rollback updates.
:-)
I think this is probably OK.
Jeff
Alan Cox wrote:
>
> > Well, maybe O_SYNC is so rare that slowdown might be acceptable.
>
> it isnt. Its a performance critical path for databases.
>
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