Caching problems while reading multiple large files...

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hi all

Some time ago, I sent a message regarding what I thought had to be the
RAID subsystem. I'm more convinced that this is the buffer cache messing
up.

scenario:

read 200 large files from disk concurrently (for instance dd of=file01
of=/dev/null, dd of=file02 of=/dev/null &c.).

As this is a 2x120g IDE RAID-0 config, I get pretty good throughtput,
eveny though I'm reading multiple files concurrently (40-50 megs per sec).

But...At the time I've read ~800 megs of data (which is the same amount as
the free memory before I start), it suddenly slows down to a mere 1 meg
per sec.

But... If I try doing another i/o operation, even to the same block
device, it works fine.

Can anyone help me out here?

roy

--
Roy Sigurd Karlsbakk, MCSE, MCNE, CLS, LCA
Computers are like air conditioners.
They stop working when you open Windows.
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• Next message: Russell King: "Re: Total system lockup with Alt-SysRQ-L"
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This archive was generated by hypermail 2b29 : Mon Dec 31 2001 - 21:00:09 EST