On 02/07/2010 17:56, Lutz Schumann wrote:
I don't know about the rest of your test, but writing
zeroes to a ZFS
filesystem is probably not a very good test, because
ZFS recognizes
these blocks of zeroes and doesn't actually write
anything. Unless
maybe encryption is on, but maybe not even then.
Not true. If I want ZFS to write zeros, ZFS does write zeros. You can simply check this
by doing a dd. ZFS does not filter "zero" writes.
Actually it does if you have compression turned on and the blocks
compress away to 0 bytes.
See
http://src.opensolaris.org/source/xref/onnv/onnv-gate/usr/src/uts/common/fs/zfs/zio.c#zio_write_bp_init
Specifically line 1005:
1005 if (psize == 0) {
1006 zio->io_pipeline = ZIO_INTERLOCK_PIPELINE;
1007 } else {
--
Darren J Moffat
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