[Redis] Connection loss after update form 2.2 to 2.6.10

Howdy,

we recently updated three redis nodes and since the update are experiencing
some strange connection problems:

In high load times the instances refuse new connections for about 1 minute.
This happens about once an hour. But not every hour and the gap is not
exactly 60 minutes.

We set maxclients to 32k and also the max open files limit in ubuntu is
32k. There are between 6k and 11k clients on average. We have ~25k commands
per second.

There are no entries in the slowlog corresponding with the connection drops.

As it happens on all three nodes at the same time i think we might hit
another limit. Is there anything known?

Thanks,

David