[CentOS] Too much memory cache being used while moving large file

[Bryan J. Smith]

Sean O Sullivan <seanos at seanos.net> wrote:
> System :
> CentOS 4.2
> 2.6.9-22.0.1.ELsmp
> System fully up-to-date.
> 3GB RAM
> 3ware 9000S card, with Raid5 array.
> I think that's about all relevant info ...

You have the latest 9.2.1.1 3Ware firmware release, correct?
And the latest driver for that release, correct?

> Had file on disk (not array), attempted to mv file to
> array. Went fine till 2.4GB was copied, then it slowed down
> to a meg every few minutes.  Free memory was ~50MB
> (Typically is 1.5-2GB), and cache was 2.5GB.
> Stopped the move, however cache not being cleared out --
> and this issue continues to happen - unsure if it was
> always a problem/known issue, it does however only occur
when
> copying a single file > 2.4GB (I have copied 5+GB of 1+GB
> files in the past without issue).

Hit the 3Ware's knowlegebse on tweaking the kernel buffer
settings for your configuration.  They are extremely
helpful/useful in this regard.  You might have to play with a
few settings before it works the most ideal.

> Also, saw following in dmesg while this was going on:
> Out of Memory: Killed process 12467 (mysqld).
> I'll be restarting server later on tonight, which will
> 'fix' immediate problem, however just curious on thoughts
> in regards to this.

Again, everytime I run into this, I hit 3Ware's knowlegebase
and find some settings that I play with and they not only
solve the problem, but increase performance.  And if it
persists, you'll be ready to talk to their tech support.

A good whitepaper to read on 3Ware 9000 series cards on
kernel 2.6 (applicable to your CentOS 4.2 system) is here:  
  http://www.3ware.com/kb/attachments/Linux2.6WP_0701.pdf  


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