Re: Advice: Hardware vs. Software RAID5

[David Brodbeck <brodbd@u.washington.edu>]

On Jan 15, 2008, at 6:14 PM, Gregory Seidman wrote:

> On Tue, Jan 15, 2008 at 03:40:15PM -0800, tofu.oni@gmail.com wrote:
> > On Jan 15, 9:10 am, Gregory Seidman <gsslist
> > +deb...@anthropohedron.net> wrote:
> > > anything that
> > > kills your motherboard (short circuit in the memory, CPU  
> > > overheating, etc.)
> > > also takes out your RAID controller. To be able to access your  
> > > data you'll
> > > need the same RAID controller
> >
> > doh!  I hadn't thought of that.  Thanks.  Software it is!
> >
> > I have an existing setup that uses four 120G drives in software  
> > RAID 5
> > under windows 2000, and I learned that it's best to have exactly the
> > same kind of drives.  Mixing WD and Seagate caused problems.  Is that
> > a RAID 5 idiosyncrasy or a windows thing?
>
> I've heard it recommended for any RAID, but I've never had a problem  
> under
> Linux sw RAID with differing brands of drives.

Two drives from different manufacturers that are the same advertised  
size may not have exactly the same formatted size.  This isn't a  
problem when you create an array; the extra space on the slightly  
larger drives is just wasted.  It can be a problem if you have a  
failed disk and the replacement drive is slightly smaller than the  
others, however.

3ware SATA RAID controllers get around this by reducing the size of  
all the drives down to some safe value, to ensure they'll all have the  
same apparent size.