On Thu, Feb 12, 2009 at 08:21:12PM +1100, NeilBrown wrote:

On Thu, February 12, 2009 7:11 pm, Keld Jørn Simonsen wrote:

quoted

On Thu, Feb 12, 2009 at 02:10:10PM +1100, NeilBrown wrote:

quoted

Comments and testing very welcome.

I would rather have functionality to convert raid10 to raid5.
raid1 should be depreciated, as raid10,n2 for all purposes is the same
but better implementation and performance, and raid10,f2 and raid10,o2
are even better.  Nobody should use raid1 anymore.

That is a fairly simplistic view.

It was also formulated to provoke some thoughts.

raid1 supports --write-mostly and --write-behind which raid10 is unlikely
ever to support.

why?

Anyway would it not be possible that this functionality be implemented
for raid10,n2?

Certainly in many cases raid10 is just as good or better than raid1
though.

Certainly a raid10->raid5 conversion for a 2-drive n2 configuration
is trivial to arrange.  Other conversions are less likely to be supported
as they require significant non-trivial rearrangement of data.

Yes, possibly.


Some code to grow raid10 would also be desirable. Maybe it is some of
the same operations that need to be applied: getting the old data in,
have it restructured for the new format, in a safe way, and possibly
with the help of an extra disk, or possibly not. It sounds non-trivial
to me too.

Best regards
keld
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