current zfs tuning in RELENG_7 (AMD64) suggestions ?

[Mike Tancsa]

I gave the AMD64 version of 7.2 RC2 a spin and all installed as 
expected off the dvd

INTEL S3200SHV MB, Core2Duo, 4G of RAM

In the past it had been suggested that for zfs tuning, something like

vm.kmem_size_max="1073741824"
vm.kmem_size="1073741824"
vfs.zfs.prefetch_disable=1

However doing a simple test with bonnie and dd, there does not seem 
to be very much difference in 4 configs.  Am I better off just with 
the defaults ?  The machine is acting as anoffline storage site, so a 
steady stream of data via rsync/ssh

The writes are all within the normal variance of the tests except for 
b).  Is there anything else that should be tuned ? Not that I am 
looking for any "magic bullets" but I just want to run this backup 
server as best as possible

               -------Sequential Output-------- ---Sequential Input-- 
--Random--
               -Per Char- --Block--- -Rewrite-- -Per Char- --Block--- 
--Seeks---
           MB K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU  /sec %CPU
a        5000  98772 54.7 153111 31.5 100015 21.1 178730 85.3 368782 
32.5 161.6  0.6
b        5000 101271 57.9 154765 31.5  61325 13.9 176741 84.6 372477 
32.8 149.3  0.6
c        5000 102331 57.1 159559 29.5 105767 17.4 144410 63.8 299317 
19.9 167.9  0.6
d        5000 107308 58.6 175004 32.4 117926 18.8 143657 63.4 305126 
20.0 167.6  0.6


a) defaults
b) vm.kmem_size_max="1073741824" vm.kmem_size="1073741824"
c) vfs.zfs.prefetch_disable=1 plus b)
d) vfs.zfs.zil_disable="1" plus c) plus b)



Results tend to fluctuate a bit.

offsitetmp# dd if=/dev/zero of=/tank1/test bs=2048k count=1000
1000+0 records in
1000+0 records out
2097152000 bytes transferred in 10.016818 secs (209363092 bytes/sec)
offsitetmp#
offsitetmp# dd if=/dev/zero of=/tank1/test bs=2048k count=1000
1000+0 records in
1000+0 records out
2097152000 bytes transferred in 10.733547 secs (195382943 bytes/sec)
offsitetmp#

Drives are raidz

ad1: 1430799MB <Seagate ST31500341AS CC1H> at ata3-master SATA300
ad2: 1430799MB <Seagate ST31500341AS CC1H> at ata4-master SATA300
ad3: 1430799MB <Seagate ST31500341AS CC1H> at ata5-master SATA300
ad4: 1430799MB <Seagate ST31500341AS CC1H> at ata6-master SATA300

on ich9

         ---Mike



--------------------------------------------------------------------
Mike Tancsa,                                      tel +1 519 651 3400
Sentex Communications,                            mike at sentex.net
Providing Internet since 1994                    www.sentex.net
Cambridge, Ontario Canada                         www.sentex.net/mike