[OmniOS-discuss] FW: Fibre Channel performance on OmniOS

[Bob Friesenhahn]

On Wed, 20 Aug 2014, Kyle Bruene wrote:

> 
> I’ve tried different pool configurations. Currently I have two pools: the 5 ssd’s in a raidz and the 3TB’s
> in a raidz. I get the same result from both because the cache is so large. With sync off, I get the same
> speed on both pools because it is just writing/reading to/from ram. I feel like there is enough hardware and
> was hoping to get better speed than this with more SSD’s. I am assuming that if I setup some kind of
> ramdisk, I would still only get the 400MB/s over FC. Reading and writing to the pool(s) locally produces
> multiple GB/s.

What method are you using to measure throughput?  It may be that your 
setup will increase throughput with more independent data streams but 
perhaps your benchmark methodology might only be using one data 
stream.

If there is a fixed response latency somewhere (e.g. SSD sync write 
time) then single-app throughput would not likely increase as more 
parallelism is added to the hardware and topology.

Even with zfs zil disabled, the disks/SSDs need to accept writes and 
cache flushes for each transaction group.  Without these cache 
flushes, your pool would likely be toast on the first power loss or 
system panic.

Bob
-- 
Bob Friesenhahn
bfriesen at simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer,    http://www.GraphicsMagick.org/