On 5/12/06, Roch Bourbonnais - Performance Engineering <[EMAIL PROTECTED]> wrote:
From: Gregory Shaw <[EMAIL PROTECTED]> Regarding directio and quickio, is there a way with ZFS to skip the system buffer cache? I've seen big benefits for using directio when the data files have been segregated from the log files. Were the benefits coming from extra concurrency (no single writter lock)
Does DIO bypass "writter lock" on Solaris? Not on AIX, which uses CIO (concurrent I/O) to bypass managing locks at filesystem level: http://oracle.ittoolbox.com/white-papers/improving-database-performance-with-aix-concurrent-io-2582
or avoiding the extra copy to page cache
Certainly. Also to avoid VM overhead (DB does like raw devices).
or from too much readahead that is not used before pages need to be recycled.
Not sure what you mean ( avoid unnecessary readahead? )
ZFS already has the concurrency.
Interesting, would like to find more on this.
The page cache copy is really rather cheap
VM as a whole is certainly not cheap.
and I assert somewhat necessary to insure data integrity.
Not following you.
The extra readahead is somewhat of a bug in UFS (read 2 pages get a maxcontig chunk (1MB)).
Ouch.
ZFS is new, conventional wisdom, may or may not apply.
This (zfs-discuss) is the place where we can be enlightened :-) Tao _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
