Jesper Krogh wrote:
> Can you point to some ZFS docs that tell that this is the case.. I'd
> be surprised
> if it doesnt copy away the old block and replaces it with the new one
> in-place. The
> other behaviour would quite quickly lead to a hugely fragmented
> filesystem that
> performs next to useless and ZFS doesnt seem to be in that category..
http://all-unix.blogspot.com/2007/03/zfs-cow-and-relate-features.html
"Blocks containing active data are never overwritten in place; instead,
a new block is allocated, modified data is written to it, and then any
metadata blocks referencing it are similarly read, reallocated, and
written."
http://opensolaris.org/jive/thread.jspa?messageID=19264 discusses how
this interacts with the common types of hardware around: no guaratees
with lying hard drives as always, but otherwise you're fine.
--
Greg Smith 2ndQuadrant US greg@2ndQuadrant.com Baltimore, MD
PostgreSQL Training, Services and Support www.2ndQuadrant.us
"PostgreSQL 9.0 High Performance": http://www.2ndQuadrant.com/books
