On Thu, February 12, 2009 8:53 pm, Keld Jørn Simonsen wrote:

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

quoted

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.

quoted

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?

It would be possible, but it might not be sensible.

write-mostly and write-behind only really make sense when you have the
clear distinction between drives that raid1 gives you.
These options don't make sense for raid10 in general.  Only in very specific
layouts.
If you like, raid1 is an implementation of a specific raid10 layout,
where it makes sense to add some extra functionality.

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.

What particular growth scenarios are you interested it?
Just adding a drive and restriping onto that?  i.e keep that
same nominal layout but increase 'raid-disks'?

That would be quite similar to the raid5 grow operation so it shouldn't
be too hard to achieve.
A 'grow' which changed the layout (e.g. near to far) would be a lot
harder.

NeilBrown


--
To unsubscribe from this list: send the line "unsubscribe linux-raid" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html