On Mon, Apr 30, 2012 at 4:15 PM, Ray Van Dolson <rvandol...@esri.com> wrote:

> I'm trying to run some IOzone benchmarking on a new system to get a
> feel for baseline performance.

    If you have compression turned on (and I highly recommend turning
it on if you have the CPU power to handle it), the IOzone data will be
flawed. I did not look deeper into it, but the data that IOzone uses
compresses very, very well. Much more so than any real data out there.
I used a combination of Filebench and Oracle's Orion to test ZFS
performance. Recently I started writing my own utilities for testing,
as _none_ of the existing offerings tested what I needed (lots and
lots of small, less than 64KB, files). My tool is only OK for relative

> Unfortunately, the system has a lot of memory (144GB), but I have some
> time so am approaching my runs as follows:

     When I was testing systems with more RAM than I wanted (when does
that ever happen :-), I called the ARC to something rational (2GB, 4GB
etc) and ran the tests with file sizes four times the ARC limit.
Unfortunately, the siwiki site appears to be down (gone ???).

On Solaris 10, the following in /etc/system (and a reboot) will cap
the zfa arc to the amount of RAM specified (in bytes). Not sure on
Nextena (and I have not had to cap the arc on my Nexenta Core system
at home).

set zfs:zfs_arc_max = 4294967296

> Throughput:
>    iozone -m -t 8 -T -r 128k -o -s 36G -R -b bigfile.xls
>    iozone -O -i 0 -i 1 -i 2 -e -+n -r 128K -s 288G > iops.txt
> Not sure what I gain/lose by using threads or not.

    IOzone without threads is single threaded and will demonstrate the
performance a single user or application will achieve. When you use
threads in IOzone you see performance for N simultaneous users (or
applications). In my experience, the knee in the performance vs. # of
threads curve happens somewhere between one and two times the number
of CPUs in the system. In other words, with a 16 CPU system,
performance scales linearly as the number of threads increases until
you get to somewhere between 16 and 32. At that point the performance
will start flattening out and eventually _decreases_ as you add more

     Using multiple threads (or processes or clients or etc.) is a
good way to measure how many simultaneous users your system can handle
(at a certain performance level).

> Am I off on this?
> System is a 240x2TB (7200RPM) system in 20 Dell MD1200 JBODs.  16 vdevs of 15
> disks each -- RAIDZ3.  NexentaStor 3.1.2.

Paul Kraus
-> Senior Systems Architect, Garnet River ( http://www.garnetriver.com/ )
-> Assistant Technical Director, LoneStarCon 3 (http://lonestarcon3.org/)
-> Sound Coordinator, Schenectady Light Opera Company (
http://www.sloctheater.org/ )
-> Technical Advisor, Troy Civic Theatre Company
-> Technical Advisor, RPI Players
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