Comments on: Direct I/O for Solaris benchmarking

By: Kevin Closson

Kevin Closson — Mon, 14 Nov 2011 17:58:58 +0000

Kyle,

Perhaps your readers might consider pushing directio onto an existing file with the code offered at the following link? Probably won’t work with ZFS…don’t know…

http://kevinclosson.wordpress.com/2007/01/11/analysis-and-workaround-for-the-solaris-10203-patchset-problem-on-vxfs-files/

By: Kevin Closson

Kevin Closson — Mon, 26 Sep 2011 16:27:48 +0000

OK, Kyle, I sort of thought that may be the case. There’s one issue that comes to mind. For production purposes customers should be running dNFS against a Filer and logging in to a filer to fiddle with dd(1) is a problem. I think you are mostly discussing the Sun S7000 (Amber Roads) in this particular case. I can’t think of any other production-quality Filer that lets one spelunk about with a full-featured shell. Am I missing the point?

I have a dd(1) from the GNU source around here somewhere that uses Solaris directio(3C) which would allow you to read the UFS files in the direct I/O path at least. I’ll see if I can rummage it up. I hacked that out whilst blogging about cp(1) on Solaris (http://kevinclosson.wordpress.com/2007/02/23/standard-file-utilities-with-direct-io/)

By: Kyle Hailey

Kyle Hailey — Mon, 26 Sep 2011 14:59:49 +0000

filesystem vs disks – yes, tests is for testing disk primarily.
My main goal in the above tests is testing the underlying disks to see whether they are the bottleneck. I’m dealing with Oracle databases over NFS so easiest thing is to go through the stack – disks, filesystem (zfs), nfs, tcp, network, host machine (cpu, memory) to the database (I/O read or write, CPU, other waits)
If the underlying areas can be isolated and tested it makes understanding the performance of the stack much easier.

By: Kevin Closson

Kevin Closson — Sun, 25 Sep 2011 23:09:09 +0000

ok…getspeed1() still won’t work without a back after the pipe…I’d just join the nawk line up

…anyway, I still push the point that you are not testing the file system be it UFS ZFS or XYZ when pounding the underlying disks… that is a good way to see what the drives can do but tells you nothing about what the file system can do…

By: Kyle Hailey

Kyle Hailey — Sun, 25 Sep 2011 17:07:53 +0000

Hey Kevin,
Thanks for stopping by and sorry for the mucked up script. Yes – something when wrong with the posting. Looks like wordpress gets in and mucks with stuff even between

. Ugh!

RE ZFS and UFS: I do most of my work on ZFS which doesn’t have direct I/O so it’s nice to have a way to run I/O benchmarks from disk with out having to mess with the pools.
I also do some tests with UFS and since dd doesn’t have direct I/O flag like on LINUX its nice to have a way to run dd with direct I/O without the flag.
- Kyle

By: Kevin Closson

Kevin Closson — Sat, 24 Sep 2011 20:31:29 +0000

disks= line is also missing the closing command quote and is followed by a stray closed parenthsis. Must be a bad paste of a korn function.

By: Kevin Closson

Kevin Closson — Sat, 24 Sep 2011 19:07:02 +0000

Hi Kyle,

This script cannot work cut-and-pastewise… the pipe to nawk following a new line would not work (just back it with “\”).

Is getspeed1 (executed inside the getspeed() ksh function) an executable in the PATH of the process executing this script? I’m not a sol expert so maybe there is a /bin/getspeed1? Seems unlikely.

Also, how does reading the raw disks under a file system help compare UFS to ZFS in any way? Maybe I’m missing the point?

P.S., I’m so glad you joined us for beers the other night…yet another OakTable moment :-)