Re: changing raid level?

[Greg Oster <oster%cs.usask.ca@localhost>]

Manuel Bouyer writes:
> On Tue, Jan 27, 2009 at 01:23:37PM -0600, Greg Oster wrote:
> >   [...]
> > 
> > For a RAID 1 set, the "parity unit" is simply the second disk, and 
> > computing that parity requires no further computations.
> 
> On a slow CPU the read+read+compare+write is killing the whole system
> (mostly the "compare" I think) with 90% of the cpu working on this.
> A simple read+write is much, much better on such a setup (the system
> is still useable while doing a raid1 reconstruct). It matters
> even on a fast CPU, when both disks are able to provide data at 180MB/s.
> The system is still useable but comptationnal tasks (esp. network
> encryption) is much, much slower.

What should happen here is that RAIDframe should have a tweakable 
sysctl knob (or something) to adjust the rebuild rate.  It's on the 
TODO list, but has never reached any sort of priority level where 
it's gotten done :(  

Later...

Greg Oster