> On Thu, 24 May 2007, MC wrote:
> 
> > An advantage Linux has over both Solaris and
> Windows is that Linux 
> > software RAID supports adding disks to an existing
> array.
> 
> Bzzzt...wrong answer. ZFS supports software RAID
> (zraid) and allows you to 
> toss disks at the pool in any way you want. You can
> add them in pairs and 
> mirror them, just toss them in, or do a number of
> other things with them 
> such as creating serpate pools and/or filesystems.

I don't believe that is the case.  What I'm talking about is "growing an array 
with devices".  So you have 3 disks in a raid5/raidz array, and then you add 
another disk, causing the free space on the array to grow from (3-1) disks 
worth of space to (4-1) disks worth of space.  Data is preserved across this 
growth.

Linux can achieve the above with four commands.  They amount to expanding the 
array into the extra disk, and then expanding the file system into the full 
array.  ( http://scotgate.org/?p=107 )

This topic has come up many times on the ZFS forums, and even then it is hard 
to get a straight answer.  I blame that on a non-standard vocabulary 
surrounding these topics.  Grow, array, pool, etc... lots of confusion and 
ambiguity there.  But by the end of each question thread, an authoritative 
answer shows up: 
http://www.opensolaris.org/jive/thread.jspa?messageID=108195#108195

So unless something has changed since April, only Linux (and a number of 
hardware solutions) support growing raid5 arrays with devices.
 
 
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