There is something more to consider with SSDs uses as a cache device. STEC mentions that they obtain improved reliability by employing error correction. The ZFS scrub operation is very good at testing filesystem blocks for errors by reading them. Besides corrections at the ZFS level, the SSD device could repair a weak block by moving it. The obvious way to detect failing blocks is by reading them. This means that SSDs will work well as a normal filesystem storage device.
In a write cache scenario, blocks may be written millions of times without ever being read. Unless the SSD device includes firmware which independently scrubs the blocks, or it always verifies that it can read what it just wrote (slowing the available transaction rate), the "write only" scenario will cause blocks to be written to extinction so that ultimately they can not be recovered by any error correction technique. Bob ====================================== Bob Friesenhahn [EMAIL PROTECTED], http://www.simplesystems.org/users/bfriesen/ GraphicsMagick Maintainer, http://www.GraphicsMagick.org/ _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
