Обсуждение: ZFS & disk cache
"The Solaris ZFS file system is safe with disk write-cache enabled because it issues its own disk cache flush commands" Could someone explain? would that mean that I checking the disk cache with "format -e" on Solaris is not needed if I use ZFS???? Thanks
On 2009-06-01, Scara Maccai <m_lists@yahoo.it> wrote: > > "The Solaris ZFS file system is safe with disk write-cache enabled because it issues its own disk cache flush commands" > Could someone explain? this means ZFS cofigured as described is suitable for the postgres data (and *log) directories > would that mean that I checking the disk cache with "format -e" on Solaris is not needed if I use ZFS???? you'd have to ask SUN about how well ZFS wouls handle that.
On Mon, 1 Jun 2009, Scara Maccai wrote: > "The Solaris ZFS file system is safe with disk write-cache enabled because it issues its own disk cache flush commands" > Could someone explain? There are discussion of this with more information at: http://www.solarisinternals.com/wiki/index.php/ZFS_Evil_Tuning_Guide#Cache_Flushes http://milek.blogspot.com/2008/02/2530-array-and-zfs.html http://blogs.digitar.com/jjww/2006/12/shenanigans-with-zfs-flushing-and-intelligent-arrays/ The only situation I'm aware of where ZFS may not be able to turn off the unsafe write cache inside a disk is with some of the newer SSD devices. For example, Jignesh Shah from Sun reported at the last PG East that Solaris wasn't doing the right thing to disable the write cache inside the Intel SSD devices he tested, which means they're doing write caching without a battery that could lead to database corruption. See page 13 of the presentation for http://blogs.sun.com/jkshah/entry/effects_of_flash_ssd_on for his quick note on that topic. -- * Greg Smith gsmith@gregsmith.com http://www.gregsmith.com Baltimore, MD