paper: lease drop

[michaelsevilla]

This is one example of how to build a sequencer with capabilities.

1. sharing
2. exclusivity
3. latency

This is an interesting piece of a low-level system. Capabilities are doing both exclusivity and pacing -- we need to make clearer what the aspects of a sequencer are and how can program it to optimize throughput/latency. Limit what we are trying to show here: we can control the bursts. We have one mechanism (token) -- it can be centralized or sticky; but we can use this interplay of batching. Batching should be orthogonal to exclusivity. This is a neat trick and example of the low-level storage.

Suggestion: use sequencer as it is, but have a separate system that prevents starvation.

Goal: decouple exclusivity from latency

• [x] acknowledge that the capability mechanism combines batching/exclusivity.
• [x] add graph that uses timeout OR count -- also handles failures

[michaelsevilla]

• [x] push off the word capability and replace with lease -- when we introduce CephFS start using capability.

[michaelsevilla]

• [x] add different timeouts -- so that we can control how much each client gets (QoS).

[michaelsevilla]

• [ ] failure with clients.

[michaelsevilla]

• [ ] add vertical lines to throughput graph to group OR show how much latency you're trading for throughput

[michaelsevilla]

Addressed with 575c91015a489369afb161e4d0ae7b633b5f06cd.