On Thu, 2 Apr 2009, James Mansion wrote: > Might have to give the whole disk to ZFS with Solaris to give it > confidence to enable write cache Confidence, sure, but not necessarily performance at the same time. The ZFS Kool-Aid gets bitter sometimes too, and I worry that its reputation causes people to just trust it when they should be wary. If there's anything this thread does, I hope it helps demonstrate how easy it is to discover reality doesn't match expectations at all in this very messy area. Trust No One! Keep Your Laser Handy! There's a summary of the expected happy ZFS actions at http://www.opensolaris.org/jive/thread.jspa?messageID=19264& and a good cautionary tale of unhappy ZFS behavior in this area at http://blogs.digitar.com/jjww/2006/12/shenanigans-with-zfs-flushing-and-intelligent-arrays/ and its follow-up http://blogs.digitar.com/jjww/2007/10/back-in-the-sandbox-zfs-flushing-shenanigans-revisted/ Systems with a hardware write cache are pretty common on this list, which makes the situation described there not that unlikely to run into. The official word here is at http://www.solarisinternals.com/wiki/index.php/ZFS_Evil_Tuning_Guide#FLUSH -- * Greg Smith gsmith@gregsmith.com http://www.gregsmith.com Baltimore, MD
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