With the put back of: [PSARC/2010/108] zil synchronicity
zfs datasets now have a new 'sync' property to control synchronous behaviour. The zil_disable tunable to turn synchronous requests into asynchronous requests (disable the ZIL) has been removed. For systems that use that switch on upgrade you will now see a message on booting: sorry, variable 'zil_disable' is not defined in the 'zfs' module Please update your system to use the new sync property. Here is a summary of the property: ------- The options and semantics for the zfs sync property: sync=standard This is the default option. Synchronous file system transactions (fsync, O_DSYNC, O_SYNC, etc) are written out (to the intent log) and then secondly all devices written are flushed to ensure the data is stable (not cached by device controllers). sync=always For the ultra-cautious, every file system transaction is written and flushed to stable storage by system call return. This obviously has a big performance penalty. sync=disabled Synchronous requests are disabled. File system transactions only commit to stable storage on the next DMU transaction group commit which can be many seconds. This option gives the highest performance, with no risk of corrupting the pool. However, it is very dangerous as ZFS is ignoring the synchronous transaction demands of applications such as databases or NFS. Setting sync=disabled on the currently active root or /var file system may result in out-of-spec behavior or application data loss and increased vulnerability to replay attacks. Administrators should only use this when these risks are understood. The property can be set when the dataset is created, or dynamically, and will take effect immediately. To change the property, an administrator can use the standard 'zfs' command. For example: # zfs create -o sync=disabled whirlpool/milek # zfs set sync=always whirlpool/perrin ------------------------ -- Team ZIL. It should be in build 140. For a little bit more information on it you might look at http://milek.blogspot.com/2010/05/zfs-synchronous-vs-asynchronous-io.html -- Robert Milkowski http://milek.blogspot.com _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
