On Wed, 15 Sep 2010, Brandon High wrote:
When using compression, are the on-disk record sizes determined before
or after compression is applied? In other words, if record size is set
to 128k, is that the amount of data fed into the compression engine,
or is the output size trimmed to fit? I think it's the former, but I'm
not certain.
We have been told before that the blocksize is applied to the
uncompressed data and that when compression is applied, short blocks
may be written to disk. This does not mean that the short blocks
don't start at a particular alignment. When using raidz, the zfs
blocks are already broken up into smaller chunks, using a smaller
alignment than the zfs record size. For zfs send, the data is
uncompressed to full records prior to sending.
Bob
--
Bob Friesenhahn
bfrie...@simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer,http://www.GraphicsMagick.org/
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