On 19/02/2010 15:43, Thanos Makatos wrote:
Hello.
I want to know what is the unit of compression in ZFS. Is it 4 KB or larger? Is
it tunnable?
I don't understand what you mean.
For user data ZFS compresses ZFS blocks these would be 512 bytes minimum
upto 128k maximum and depend on the configuration of the dataset
(recordsize property) and the write pattern of the applications using it.
If a block doesn't compress by more than 12.5% ZFS stores the
uncompressed data instead - note this is not tunable and is hardcoded to
the same value of all compression methods.
The only "tunnables" for compression are selecting a different
compression algorithm for the filesystem.
What problem do you think you have or are you trying to solve ?
If you read the source for the lzjb algorithm used in ZFS the lempel
size is 1k, is that what you mean ?
--
Darren J Moffat
_______________________________________________
zfs-discuss mailing list
zfs-discuss@opensolaris.org
http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
