Nicolas Williams wrote:
On Thu, Dec 03, 2009 at 12:44:16PM -0800, Per Baatrup wrote:
if any of f2..f5 have different block sizes from f1
This restriction does not sound so bad to me if this only refers to
changes to the blocksize of a particular ZFS filesystem or copying
between different ZFSes in the same pool. This can properly be managed
with a "-f" switch on the userlan app to force the copy when it would
fail.
Why expose such details?
If you have dedup on and if the file blocks and sizes align then
cat f1 f2 f3 f4 f5 > f6
will do the right thing and consume only space for new metadata.
I think Per's concern was not only with space consumed but also the effort
involved in the process (think large files); if I read his emails
correctly, he'd like what amounts to manipulation of meta-data only to have
the data blocks of what was originally 5 files to end up in one file; the
traditional concat operation will cause all the data to be read and written
back, at which point dedup will kick in, and so most of the processing has
already been spent. (Per, please correct/comment)
Michael
--
Michael Schuster http://blogs.sun.com/recursion
Recursion, n.: see 'Recursion'
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