[CentOS] Centos/Linux Disk Caching, might be OT in some ways

nate centos at linuxpowered.net
Thu Jan 28 16:37:16 UTC 2010


Les Mikesell wrote:

> I wonder if the generally-horrible handling that linux has always done
> for fsync() is the real reason Oracle spun off their own distro?  Do
> they get it better?

Anyone in their right mind with Oracle would be using ASM and direct
I/O so I don't think it was related.

http://www.oracle.com/technology/pub/articles/smiley_10gdb_install.html#asm
http://www.ixora.com.au/tips/avoid_buffered_io.htm

"The file system cache should be used to buffer non-Oracle I/O only.
Using it to attempt to enhance the caching of Oracle data just wastes
memory, and lots of it. Oracle can cache its own data much more
effectively than the operating system can. "

Which leads me back to my original response, forget about file
system cache if you want performance go for application level
caching whether it's DB caching or other caching like memcached
mentioned by someone.

Oracle did it because they wanted to control the entire stack.

nate




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