Re: PG recovery reservation state chart

[Josh Durgin <josh.durgin@inktank.com>]

On 10/02/2012 01:42 PM, Mike Ryan wrote:
> On Tue, Oct 02, 2012 at 01:35:34PM -0700, Tommi Virtanen wrote:
>> On Tue, Oct 2, 2012 at 12:48 PM, Mike Ryan <mike.ryan@inktank.com> wrote:
>>> Tried sending this earlier but it seems the list doesn't like PNGs.
>>> dotty or dot -Tpng will make short work of the .dot file I've attached.
>>
>> vger discards messages with attachments. It's old school mailing list
>> software. It's also used by many old school communities, that consider
>> this a valuable anti-spam tactic, so they're not interested in
>> changing it.
>
> I figured as much. It would have been nice to receive a notification
> that it was dropped rather than having it silently fall on the floor,
> especially since a copy of the message is not sent to the sender upon
> list acceptance. c'est la vie
>
>> Once this becomes less a design hypothetical and more a description of
>> how the code works, please please please put the dot in doc/dev/
>
> This is unnecessary, as the doc scripts will automatically generate a
> full peering state chart (of which this is just a sub state). Major
> kudos to Sam Just for making that happen!

It'd be good to update doc/dev/osd_internals with a description of the
reservations though, maybe expanding 
doc/dev/osd_internals/backfill_reservation.

One other thing I'd like to see made explicit:

How does this handle upgrades? i.e., what will happen when some OSDs
have this reservation mechanism and some do not?