[SATLUG] lvm2 and raid 0

Brad Knowles brad at shub-internet.org
Mon Jan 7 16:06:28 CST 2008


On 1/7/08, Chris Lemire wrote:

>  It should provide me with enough performance because that's where all
>  my installed applications will be and virtual appliances.

That's where you say they'll be, but how can you be sure that they're 
not going to bottleneck on storage somewhere else on the system -- 
maybe trying to do lots of transactional processing (or whatever) in 
your home directory?

Without a proper bottleneck analysis and a performance baseline, all 
you're doing is guessing.  You might as well be throwing darts in the 
dark, with a blindfold on.

Now, if you don't care whether you guess right, then why do you 
bother to guess in the first place?

>                                               I wonder if that will increase
>  my performance with it. Even with 2x core overclocked cpu, 2 gb dual
>  channel memory, sata2 drives, and a 8800 gts 320 mb, I can't run Quake 4
>  in Linux at full settings. I can run it at full settings at 1280x1024.
>  I haven't tried to see if I could do 1600x1200 with overclocking the gpu
>  using coolbits and running the game on a raid 0 device.

If you did a bottleneck analysis, you'd know whether or not there is 
any significant disk activity during Quake 4, and you'd know whether 
or not it would make any performance improvement to stripe the disks, 
or if you should be looking somewhere else.

For disk subsystem latency, try running "iostat -dx -p / 1" in the 
background (or maybe send the output of that command to a file, which 
you can then later look at with "less", or "vi", etc...), and pay 
special attention to the "avgqu-sz", "await", "svctm", and "%util" 
parameters.

There are plenty of other performance monitoring tools you can be 
looking at to see what bottlenecks you may have elsewhere in the 
system.

-- 
Brad Knowles <brad at shub-internet.org>
LinkedIn Profile: <http://tinyurl.com/y8kpxu>


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