On Sat, 19 Dec 2009 13:09:03 +0100
Jakob-Tobias Winter [off-list ref] wrote:

Hey there,

my raidsets are still using 0.91 and I might want to upgrade to the
newer metadata. - The system is running kernel 2.6.32.1 x86_64 with
mdadm v3.0.3.

0.91 is only used during a reshape - e.g. adding a device to a RAID5.
Once the reshape completes it will revert to 0.90.

Are there benefits to upgrading or should I stay with my current
metadata version?

You cannot upgrade the metadata on an array.  You can only create a new array
with new metadata.
If you create a new array with current mdadm you will get v1.1 metadata.

If what you have works, there is no need to change it.

NeilBrown