On Apr 11, 2011, at 17:54, Brandon High wrote: > I suspect that the minimum memory for most moderately sized pools is > over 16GB. There has been a lot of discussion regarding how much > memory each dedup'd block requires, and I think it was about 250-270 > bytes per block. 1TB of data (at max block size and no duplicate data) > will require about 2GB of memory to run effectively. (This seems high > to me, hopefully someone else can confirm.)
There was a thread on the topic with the subject "Newbie ZFS Question: RAM for Dedup". I think it summarized pretty well by Erik Trimble: > bottom line: 270 bytes per record > > so, for 4k record size, that works out to be 67GB per 1 TB of unique data. > 128k record size means about 2GB per 1 TB. > > dedup means buy a (big) SSD for L2ARC. http://mail.opensolaris.org/pipermail/zfs-discuss/2010-October/045720.html Remember that 270 bytes per block means you're allocating one 512-byte sector for most current disks (a 4K sector for each block RSN). See also: http://mail.opensolaris.org/pipermail/zfs-discuss/2010-March/037978.html http://mail.opensolaris.org/pipermail/zfs-discuss/2010-February/037300.html _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
