Subject: Re: comparing raid-like filesystems
To: Greg 'groggy' Lehey <>
From: Jason R Thorpe <>
List: current-users
Date: 01/31/2003 18:17:30
On Sat, Feb 01, 2003 at 12:35:45PM +1030, Greg 'groggy' Lehey wrote:

 > On Friday, 31 January 2003 at 14:18:12 -0500, Greg A. Woods wrote:
 > > [ On Friday, January 31, 2003 at 10:32:22 (-0800), Jeremy C. Reed wrote: ]
 > >> Subject: comparing raid-like filesystems (was Re: Experimental support forATA  "RAID" volumes)
 > >>
 > >> On Thu, 30 Jan 2003, Jason R Thorpe wrote:
 > >>
 > >>> I would actually prefer to see a much lighter-weight RAID implementation
 > >>> in NetBSD.
 > >>
 > >> Does one exist?
 > >
 > > No freely available RAID implementation that is "much lighter-weight"
 > > than RAIDframe exists, at least not so far as I can discover.
 > I suppose it depends on what you mean by "lighter-weight".  If you're
 > talking about CPU load, I don't think that any of the implementations
 > add much to it.

I'm mostly referring to:

	* RAIDframe's code size.  It's huge.  It's gigantic.

	* RAIDframe's over-zealous use of threads.  It makes multiple
	  context switches for each component I/O.  That's .. pathetic.

	* RAIDframe's twisty-maze of data structures.  Eek.

	* RAIDframe's multiple-implementations-of-some-things (like
	  N-way XOR), some synchronous, some asynchronous (so much
	  for adding hardware acceleration for computation of parity
	  blocks when in non-degraded mode).

Let's face it, we can do better.  RAID card vendors put RAID 0,1,5
implementations into reasonably small amounts of flash every day ..
I mean, the firmware updates fit easily onto a floppy with lots of
room to spare.  And then they proceed to run that firmware on i960s,
which aren't the fastest CPUs around.

        -- Jason R. Thorpe <>