Areca vs. ZFS performance testing.

[Danny Carroll]

Danny Carroll wrote:
> Jeremy Chadwick wrote:
>> I'd like to see the performance difference between these scenarios:
>>
>> - Memory cache enabled on Areca, write caching enabled on disks
>> - Memory cache enabled on Areca, write caching disabled on disks
>> - Memory cache disabled on Areca, write caching enabled on disks
>> - Memory cache disabled on Areca, write caching disabled on disks
>>


The initial results for a ICH9 vs Areca in JBod mode can be found here:
http://www.dannysplace.net/ZFS-JBODTests.html

Summary:
	5 Disk ZFS RaidZ array with atime turned off.
	ICH9      - block reads  avg 400MByte/Sec
	ICH9      - block writes avg 150MByte/Sec
	ArecaJBOD - block reads  avg 300MByte/Sec
	ArecaJBOD - block writes avg 160MByte/Sec


The Areca seems to be in all except char and block writes.  Block reads
are 75% as fast as the ICH9 and rewrites are about 85% as fast.

There seems to be little difference between enabling and disabling the
disk cache on the Areca.  This leads me to two conclusions:
	1. Disabling the write cache does nothing on Seagate drives.
	2. IO to the drives is so slow that a write cache is irrelevant.

These are just some quick tests that I started with, mainly to compare
the areca bus versus the ich9 bus.  If someone has any tuning
suggestions, then now is the time to make them before I migrate the ICH9
drives to the Areca bus.

-D
p.s. My OS details are:
FreeBSD 7.1-PRERELEASE #3: Tue Nov  4 13:58:49 EST 2008
localhost# cat /etc/sysctl.conf
kern.maxvnodes=400000
net.key.preferred_oldsa=0
net.key.blockacq_count=0
kern.ipc.maxsockbuf=400000
net.inet.ip.fastforwarding=1
net.inet.tcp.rfc1323=1
kern.ipc.maxsockbuf=16777216
net.local.stream.sendspace=82320
net.local.stream.recvspace=82320
net.inet.tcp.local_slowstart_flightsize=10
net.inet.tcp.nolocaltimewait=1
net.inet.tcp.delayed_ack=1
net.inet.tcp.delacktime=100
net.inet.tcp.mssdflt=1460
net.inet.tcp.sendspace=78840
net.inet.tcp.recvspace=78840
net.inet.tcp.slowstart_flightsize=54
net.inet.tcp.inflight.enable=1
net.inet.tcp.inflight.min=6144
net.inet.tcp.hostcache.expire=3900

localhost# cat /boot/loader.conf
hw.em.rxd=4096
hw.em.txd=4096
vm.kmem_size="1536M"
vm.kmem_size_max="1536M"
smb_load="YES"
smbus_load="YES"
ichsmb_load="YES"