Concurrency, again

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I performed another test on Friday for concurrency. I had 9 workstations performing an iozone througput test. Each machine ran 20 threads each processing against a 15MB file, for a total working set size of 2.7GB which fits into the server's RAM. The results from the workstations were pretty consistant. The workstations had all of 384MB of RAM in them, and the number of IOZone threads running caused significant page-faulting to occur. Which has the side effect of minimizing client-side caching. The workstations were connected to the core by way of 100MB ethernet, so maximum theoretical speeds are 12.5MB/s.

Some typical results, units are in KB/s

Initial write
Reverse Read
Stride read
Random read
Mixed workload
Random write

Consistantly, write performance is better than read performance. On the tests that are greatly benefitted by caching, reverse read and stride read, performance was quite acceptable. All nine machines wrote at near flank speed for 100MB ethernet, which means that the 1GB link the server was plugged in to was doing quite a bit of work during the Initial Write stage.

What is perhaps the most encouraging is that CPU loading on the server itself stayed below the saturation level. Having spoken with some of the engineers who write this stuff, this is not surprising. They've spent a lot of effort in making sure that incoming requests can be fulfilled from cache and not go to disk. Going to disk is more expensive in Linux than in NetWare due to architectural reasons. Had the working set been 4GB or larger I strongly suspect that CPU loading would have been significantly higher. Unfortunately, as school is back in session I can't 'borrow' that lab right now as the tests themselves consume 100% of the resources on the workstations. Students would notice that.

The next step for me is to see if I can figure out how large the 'working set' of open files on FacShare is. If it's much bigger than, say, 3.2GB we're going to need new hardware to make OES work for us. This won't be easy. A majority of the size of the open files are outlook archives (.PST files) for Facilities Management. PST files are low performance critters, so I don't care if they're slow. I do care about things like access databases, though, so figuring out what my 'active set' actually is will take some figuring.

Long story short: With OES2 and 64 bit hardware, I bet I could actually use a machine with 18GB of RAM!

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Hello -I found your site while searching for help with reading my Iozone results. I am trying to test read/write speed from an XP machine to a Netware 6.5 server over a 100MB lan. The results I get are baffling and was hoping you might have a suggestion for me.I'm to the point where I can get (I think) accurate write numbers (ex: 7000 - 9000 Kilobytes/s) However the read numbers are weird (ex: from 700000 - 1000000).This is the command line I am using: iozone -Rab 123.wks -i 0 -i 1 -+u -f z:\test\01.tmp -q 64k -n 32M -g 4G -zMy test PC has 2 gigs of ram.Guess this is more of a cry for help than a comment! Anyhow, thanks... I am enjoying the rest of your