ZFS performance on 7.2-release/amd64 low compared to UFS2 + SoftUpdates

[Dan Naumov]

I am wondering if the numbers I am seeing is something expected or is
something broken somewhere. Output of bonnie -s 1024:

on UFS2 + SoftUpdates:

              -------Sequential Output-------- ---Sequential Input-- --Random--
              -Per Char- --Block--- -Rewrite-- -Per Char- --Block--- --Seeks---
Machine    MB K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU  /sec %CPU
         1024 56431 94.5 88407 38.9 77357 53.3 64042 98.6 644511 98.6
23603.8 243.3

on ZFS:

              -------Sequential Output-------- ---Sequential Input-- --Random--
              -Per Char- --Block--- -Rewrite-- -Per Char- --Block--- --Seeks---
Machine    MB K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU  /sec %CPU
         1024 22591 53.7 45602 35.1 14770 13.2 45007 83.8 94595 28.0 102.2  1.2


atom# cat /boot/loader.conf
vm.kmem_size="1024M"
vm.kmem_size_max="1024M"
vfs.zfs.arc_max="96M"

The test isn't completely fair in that the test on UFS2 is done on a
partition that resides on the first 16gb of a 2tb disk while the zfs
test is done on the enormous 1,9tb zfs pool that comes after that
partition (same disk). Can this difference in layout make up for the
huge difference in performance or is there something else in play? The
system is an Intel Atom 330 dualcore, 2gb ram, Western Digital Green
2tb disk. Also what would be another good way to get good numbers for
comparing the performance of UFS2 vs ZFS on the same system.


Sincerely,
- Dan Naumov