Roch Bourbonnais - Performance Engineering wrote:
I'm puzzled by 2 things.Naively I'd think a write_cache should not help throughput test since the cache should fill up after which you should still be throttled by the physical drain rate. You clearly show that it helps; Anyone knows why/how a cache helps throughput ? And the second thing...quick search, this seems relevant Bug ID: 6397876 Synopsis: sata drives need default write cache controlled via property Integrated in Build: snv_38 http://bugs.opensolaris.org/bugdatabase/view_bug.do?bug_id=6397876
well, that just says that the cache settings dont stick across reboot. that doesnt seem to have any bearing on whether zfs toggles write cache or not.
From the sound of things, it sounds like what was previously written on this list was incorrect: I now infer that zfs does NOT do any "smart toggling" of write cache enable/disable on drives that it uses.
(although it may or may not do some "flush cache" calls at appropriate moments) _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
