[OmniOS-discuss] Slow performance with ZeusRAM?

[Bob Friesenhahn]

On Thu, 22 Oct 2015, Matej Zerovnik wrote:
>
> If I create a new raidz2 pool with 10 hard drives, mirrored ZeusRAMs for ZIL and set sync=always, I can only squeeze 14k IOPS out of the system.
> Is that normal or should I be getting 48k IOPS on the 2nd pool as well, since this is the performance ZeusRAM can deliver?

Is your zfs filesystem using 4k blocks?  Random writes may also 
require random reads due to COW.  If the data is not perfectly aligned 
and perfectly fill the underlying zfs block, and the existing data is 
not already cached in ARC, then it needs to be read from underlying 
store so existing data can be modified during the write.

I do see that you are using asynchronous I/O, which may add more 
factors.

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