[ale] Confusing RAID Performance

[Greg Freemyer]

Brian,

I'm curious too and went to your spreadsheet, but only the first 100
lines are showing up.  Possibly because I'm anonymous.

Can you move the fread and re-fread lines to the top of the spreadsheet?

Greg

On Wed, Feb 2, 2011 at 1:46 PM, Brian Pitts <brian at polibyte.com> wrote:
> I recently finished running iozone benchmarks comparing hardware and
> software RAID6 using 11 SATA disks on a server has 8GB of RAM.
> There was one part of the results that jumped out at me as not making
> sense. For the fread and re-fread reports, the perfomance of the
> hardware RAID increased when the test file went from 8GB to 16GB.
>
> Does anyone have a theory about why this might be?
>
> Here is the puzzling data. The top row is records sizes, the left column
> is file sizes. See how performance drops dramatically as we go from 4GB
> to 8GB, since the test file no longer fits in RAM, but then increases
> some for 16GB.
>
> Fread Report    64      128     256     512     1024    2048    4096    8192    16384
> 4194304 3499493 3559324 3485319 3338358 3353441 2864384 1614729 1537980
> 1469821
> 8388608 220831  216510  232010  325999  327661  332615  356501  357100  321870
> 16777216        644804  644335  629204  506989  624378  595963  596668  606618  652013
>
> Re-fread Report 64      128     256     512     1024    2048    4096    8192    16384
> 4194304 3501556 3563106 3509425 3339554 3364700 3123160 1611168 1535767
> 1533804
> 8388608 234456  226453  242365  381102  386371  407422  389960  442331  384986
> 16777216        688988  688057  686493  686028  683425  687335  687437  686031  689457
>
> The definition of the fread test is "this test measures the performance
> of reading a file using the library function fread(). This
> is a library routine that performs buffered & blocked read operations.
> The buffer is within the user’s address space."
>
> I have more of the iozone output in this publicly-viewable spreadsheet
> if anyone cares to take a look at the rest of the results.
>
> https://spreadsheets.google.com/a/apidb.org/ccc?key=0AoW4-KM82tL9dDV3a3NMUmZ0aWozaFh6RWFRUGdaakE&hl=en&ndplr=1#gid=0
>
> --
> All the best,
> Brian Pitts
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-- 
Greg Freemyer
Head of EDD Tape Extraction and Processing team
Litigation Triage Solutions Specialist
http://www.linkedin.com/in/gregfreemyer
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   http://insession.blogs.cnn.com/2010/03/23/how-computer-evidence-gets-retrieved/

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