D&C GLug - Home Page

[ Date Index ] [ Thread Index ] [ <= Previous by date / thread ] [ Next by date / thread => ]

Re: [LUG] File system for heavy I/O

 

On 24/03/14 23:25, Martijn Grooten wrote:
> 
> I have to say, the performance improvements were a little disappointing.
> Which probably shows I'm still doing something seriously wrong
> somewhere.

If there is a small working set and the writes are not blocking, then it
is probably in RAM anyway, so tmpfs is going to have little benefit, and
potentially negative since you probably made a suboptimal split compared
to the kernel.

I'd always benchmark such a system with bonnie++, and compare that to
expected performance of the IO system, just to sanity check it, but
beyond that you want specific ideas of what is slow.

Ponder the rationale behind design of Varnish, your kernel does know how
to efficiently read files from disk, and write them to disk, it might
not be tuned to your specific case but it is probably good enough.

It probably worth thinking about how/what you are doing, rather than how
the system is configured. Unless you know already you are doing
something silly.

Only times I've seen IO bottleneck recently on even fairly low end
modern hardware has nearly always been when it is rewriting files in a
loop. e.g. Write out file with data A in, modify A, write out whole file
again, rinse repeat.

Sure there are situations where you know it will be a lot of data, but
these nearly always from grubby low level systems, be it instrument
data, or network monitoring, and often here it pays to ask - do I need
everything.


-- 
The Mailing List for the Devon & Cornwall LUG
http://mailman.dclug.org.uk/listinfo/list
FAQ: http://www.dcglug.org.uk/listfaq