On 2003-01-24 21:58:55 -0500, Tom Lane wrote:
> The key assumption we are making about the filesystem's behavior is that
> writes scheduled by the sync() will occur before the pg_control write
> that's issued after it. People have occasionally faulted this algorithm
> by quoting the sync() man page, which saith (in the Gospel According To
> HP)
>
> The writing, although scheduled, is not necessarily complete upon
> return from sync.
>
> This, however, is not a problem in itself. What we need to know is
> whether the filesystem will allow writes issued after the sync() to
> complete before those "scheduled" by the sync().
>
Certain linux 2.4.* kernels (not sure which, newer ones don't seem to have
it) have the following kernel config option:
Use the NOOP Elevator (WARNING)
CONFIG_BLK_DEV_ELEVATOR_NOOP
If you are using a raid class top-level driver above the ATA/IDE core,
one may find a performance boost by preventing a merging and re-sorting
of the new requests.
If unsure, say N.
If one were certain his OS wouldn't do any re-ordering of writes, would it be
safe to run with fsync = off? (not that I'm going to try this, but I'm just
curious)
Vincent van Leeuwen
Media Design
