Mnesia disk performance (was RE: multi-attribute mnesia indexes?)

[David Gould]

On Wed, Jan 03, 2001 at 10:08:25AM +0100, Ulf Wiger wrote:
> 
> I must confess that I haven't kept up with OS vs DBMS design in the
> past few years, but it used to be commonly accepted that you simply
> couldn't build a really fast DBMS on top of the standard file and
> memory management provided by the leading operating systems --
> certainly not if you wanted similar behaviour across multiple
> platforms. I don't know if it's still true...

Mostly still true in the hardcore DBMS world, but better/easier than it
used to be.
 
> choice upon installing the database whether you wanted it to reside on
> a normal file system (good for testing) or on a raw partition (good
> for speed). In the case of the raw partition, SUPRA would use its own
> file I/O driver.

This is still common, it depends really on whether the OS provides both
unbuffered and asynchronous I/O to files (eg, VMS, NT, some unix), or
only to raw disks (eg, some unix, current Linux (work in progress)).

The real issue is unbuffered and asynch I/O, DBMSs are happy to use
a filesystem if it can provide these features.

-dg

-- 
David Gould                                                 dg@REDACTED
SuSE, Inc.,  580 2cd St. #210,  Oakland, CA 94607          510.628.3380
why would you want to own /dev/null? "ooo! ooo! look! i stole nothing!
i'm the thief of nihilism! i'm the new god of zen monks."