> 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 { >
Interesting, did quick test: Writing zeros async: Dedup=on, Compression=off -> 60 MB / sec Writing zeros async: Dedup=off, Compression=on -> 480 MB /sec Writing zeros async: Dedup=off, Compression=off -> 12 MB / sec It seems if I do a sync write with dedup=off, compress=on, I get 12 MB / sec. In both cases I see disk /IO. So for me itlooks like meta data writes - the I/O beeing limited to 480 Mb/s seems to be limited by the async meta data updates (this is a VM, so slow). So does that mean that zero data blocks are not written, but meta data blocks ? Robert -- This message posted from opensolaris.org _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
