On Tue, 30 Jun 2009, Richard Elling wrote:
UFS has a relatively small write buffer and ZFS could consume up to 1/8 of memory for writes (located in the ARC). There is some question about whether 1/8 of memory is a good guess. Anecdotal evidence suggests that there are cases where the 1/8 limit is too large when you have lots of memory and slow disks. If a better rule can be defined, I'm sure it would be welcome in the code.
Are you sure that 1/8 of memory is what ZFS is really using? Playing with setting zfs_write_limit_override causes me to believe that it is really 7/8ths of maximum ARC memory (or more!). The largest zfs_write_limit_override value I can set on my 20GB system with 10GB ARC cap is around 8053063680 and it still clearly does not send nearly as much data to the storage array as the system default. Now I am thinking that it is using a cap much bigger than 10 GB, and is perhaps using 16GB.
I sense a bug in Solaris 10 here ... Bob -- Bob Friesenhahn bfrie...@simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/ GraphicsMagick Maintainer, http://www.GraphicsMagick.org/ _______________________________________________ perf-discuss mailing list perf-discuss@opensolaris.org
