[sles-beta] SLES Storage / MD RAID feature

[Decker Maximilian]

Hi list,

maybe someone at SuSE is also able to give some comments on this one.

Background is:

When migrating Unix-Systems to the Linux platform, especially with HP-UX being the source,
there seems to be one very specific drawback concerning LVM and logical disk mirrors.

Let's say if I wanted to have LVM'ed filesystems (non-clustered, i.e. like ext3) and want them
deployed as RAID 1 mirror at two dedicated storage systems (or even datacenters), one option 
would be to use host based RAID 1 instead of a more expensive und less flexible storage mirror.
(with flexible I mean "not to be vendor locked with future upgrades")

General recommendation in Linux land (AFAIK) sees LVM for just the volume pools and MD as the 
RAID layer (so no LVM RAID).

Syncing (esp. re-syncing) the mirror has improved dramatically with the introduction of the
write-intent bitmap. But there is one thing that would be really nice to have, and I wonder if
there are any plans for SLES to actually provide that in the future:

With lvdisplay -v on HP-UX you can get the full list of all the logical extents showing their state,
which can be "current" or "stale". In case of a "stale" extent, re-sycing that specific extent is 
possible. In any case, you get a great and detailed overview on the status of the RAID mirror.
Of course the system has to keep track of that list, meaning some kind of database is needed,
thus resulting in a bit of performance penalty. (->/etc/lvmconf/* on HP-UX)

So, long story short - something like this already on the SLES roadmap ?
Or maybe already there and I just missed it ?
(/proc/mdstat only shows a very generic form of status display here)


And yes, if not, well it actually is some kind of feature request then ;-)



thanks,

- Maximilian