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@xxxxxxxxxxxxxxx Baltimore, MD
PostgreSQL Training, Services and Support www.2ndQuadrant.us
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