Thanks Jason, thanks Dan,

On 9 March 2016 at 01:34, Jason Dillaman <[email protected]> wrote:
> Are you interesting in the max FD count or max thread count?  You mention 
> both in your email.

True, I did mix the two somewhat incorrectly - I was sort of guessing
there'd be some number of threads per socket or vice versa. I really
should have made the subject "file/socket requirements for librbd",
because in practice it's the FDs that we actually care about as both
RedHat and Ubuntu default max_files soft ulimit seems to be quite low
compared to all others. What still gripes me is that qemu doesn't seem
to handle the error at all gracefully, i.e., not even an error logged
- but perhaps that is actually up to librbd and could indicate a bug
there?

> Right now qemu doesn't pool OSD connections when you have multiple RBD images 
> connected to the same VM -- each image uses its own librbd/librados instance. 
>  Since each image, at the worst case, might have to connect to each OSD and 
> MON, that should be enough to determine the rough upper bound that you will 
> require for qemu (e.g. 3 MONs, 1000 OSDs, max 10 RBD images per VM == roughly 
> 10,000 socket connections worse case).

Great, that's the sort of rough formula I was after - thank-you!

-- 
Cheers,
~Blairo
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