On Mon, Feb 7, 2011 at 10:29 AM, Yi Zhang <yizhan...@gmail.com> wrote: > I already set primarycache to metadata, and I'm not concerned about > caching reads, but caching writes. It appears writes are indeed cached > judging from the time of 2.a) compared to UFS+directio. More > specifically, 80MB/2s=40MB/s (UFS+directio) looks realistic while > 80MB/0.11s=800MB/s (ZFS+primarycache=metadata) doesn't.
You're trying to force a solution that isn't relevant for the situation. ZFS is not UFS, and solutions that are required for UFS to work correctly are not needed with ZFS. Yes, writes are cached, but all the POSIX requirements for synchronous IO are met by the ZIL. As long as your storage devices, be they SAN, DAS or somewhere in between respect cache flushes, you're fine. If you need more performance, use a slog device that respects cache flushes. You don't need to worry about whether writes are being cached, because any data that is written synchronously will be committed to stable storage before the write returns. -B -- Brandon High : bh...@freaks.com _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
