On Mon, 19 Apr 2010, Edward Ned Harvey wrote:
Improbability assessment aside, suppose you use something like the DDRDrive X1 ... Which might be more like 4G instead of 32G ... Is it even physically possible to write 4G to any device in less than 10 seconds? Remember, to achieve worst case, highest demand on ZIL log device, these would all have to be <32kbyte writes (default configuration), because larger writes will go directly to primary storage, with only the intent landing on the ZIL.
Note that ZFS always writes data in order so I believe that the statement "larger writes will go directly to primary storage" really should be "larger writes will go directly to the ZIL implemented in primary storage (which always exists)". Otherwise, ZFS would need to write a new TXG whenever a new "large" block of data appeared (which may be puny as far as the underlying store is concerned) in order to assure proper ordering. This would result in a very high TXG issue rate. Pool fragmentation would be increased.
I am sure that someone will correct me if this is wrong. Bob -- Bob Friesenhahn bfrie...@simple.dallas.tx.us, 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
