On Tue, Dec 3, 2013 at 5:49 AM, Bjoern Gruening <bjoern.gruening@gmail.com> wrote:

The new discs will be type="distributed" id="primary" and the old disc
will become type="disk" id="secondary". If I understood correctly the
old disc is them in some read-only state and will not touched until the
primary discs are full or not working ...

Correct -- the default HierarchicalObjectStore always writes new files to the first ObjectStore but can read through to any of them. Probably worth noting that, with this base implementation (that could easily be extended to do whatever you'd prefer), when the first objectstore gets full it still won't attempt to write to the second.

Is it save to mount the old discs or all discs with noatime, to get a
small performance gain? Is Galaxy using noatime?

I do believe we're using it, but Nate would be better able to comment on the actual performance gain we see.