>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.
There's a difference between "written" and "the data is referenced by the uberblock". There is no need to start a new TXG when a large datablock is written. (If the system resets, the data will be on disk but not referenced and is lost unless the TXG it belongs to is comitted) Casper _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
