[PLUG] non-buffered I/O in Linux?

[Andrew Puch]

On Mon, 2002-06-03 at 22:18, Alex Daniloff wrote:
> Hello Linux folkz,
> Does somebody know if Linux kernel allows to perform non-buffered I/O on raw 
> disk partitions?
> In documentation on InnoDB tables it said:
> By using a raw disk you can on some Unixes perform unbuffered I/O.
> I assume that it should improve DB performance.
maybe, sun has run bench marks of both. 

See sun solars performance, red 911 car book. 

In some cases, sun found that data base improved with the normal file
system tweaked for database.  

A normal file system is a hell of a lot easier to deal with, I would
only go to raw partitions if I did not have to deal with the PAIN of
back ups. Or had a happy oracle tool, to grab the raw data. 

I have talk to many a oracle dba, and they have said the same. 


Do you have big DLT tape drive. 

It is far far easier to loose all of your data with raw partions. 

The free databases are no oracle / db2 as far as tool chain to back up
your data.

You are looking at, database shut down, dump the raw partitions. 

Wait a long time, hours , etc. 

> Thank you in advance for any thoughts or sources of information.
> Alex

 SGI was the 1st do this work 

here are a few links, 

POSIX Asynchronous I/O 
http://oss.sgi.com/projects/kaio/

Raw IO 
http://oss.sgi.com/projects/rawio/news.html


This is what you want. 

http://tldp.org/HOWTO/IO-Perf-HOWTO/x159.html
http://lists.sourceforge.net/lists/listinfo/kiobuf-io-devel
http://www.itworld.com/nl/lnx_tip/10122001/