CTDB scaling?

[Richard Sharpe]

On Thu, Nov 20, 2014 at 10:19 AM, ronnie sahlberg
<ronniesahlberg at gmail.com> wrote:
> On Thu, Nov 20, 2014 at 9:33 AM, Richard Sharpe
> <realrichardsharpe at gmail.com> wrote:
>> That would make more sense. Then, in the one node case we were hitting
>> the one node limit, and as you say, with two nodes and the load
>> divided between them, more memory was available for caching so we see
>> a big boost there. After that, we seem to be hitting the IO limit of
>> the cluster because more memory does not seem to help that much ... By
>> the time we hit six nodes it looks like we would probably be seeing
>> only another 20MB/s or less for the additional nodes.
>
> Probably.
> I think I recall that tridge might have done these very early tests on
> virtual machines running under QEMU/KVM
> thus making the actual numbers even more difficult to parse/meaningless.
>
> I think the only real takeaway from these numbers is that "scaling is
> good for that kind of workload".
>
> Later tests on real hardware showed for uncontended cases pretty much
> linear scaling up to ~30 nodes
> all pretty much saturating 10GbE on each node in CIFS traffic.
> For the uncontended case.
>
> The heavily contended case often did not scale well at all. Later
> additions to the protocol such as sticky records and
> read-only record delegations helped for some, not nearly all,
> workloads but I do not know if any performance numbers were ever
> collected on that.

Is any of this documented other than in the code?

-- 
Regards,
Richard Sharpe
(何以解憂？唯有杜康。--曹操)