On Fri, Jun 4, 2010 at 12:37 PM, Ray Van Dolson <[email protected]> wrote: > Makes sense. So, as someone else suggested, decreasing my block size > may improve the deduplication ratio.
It might. It might make your performance tank, too. Decreasing the block size increases the size of the dedup table (DDT). Every entry in the DDT uses somewhere around 250-270 bytes. If the DDT gets too large to fit in memory, it will have to be read from disk, which will destroy any sort of write performance (although a L2ARC on SSD can help) If you move to 64k blocks, you'll double the DDT size and may not actually increase your ratio. Moving to 8k blocks will increase your DDT by a factor of 16, and still may not help. Changing the recordsize will not affect files that are already in the dataset. You'll have to recopy them to re-write with the smaller block size. -B -- Brandon High : [email protected] _______________________________________________ zfs-discuss mailing list [email protected] http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
