Subject: Re: comparing raid-like filesystems
To: Greg 'groggy' Lehey <email@example.com>
From: Jason R Thorpe <firstname.lastname@example.org>
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 <email@example.com>