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Barcelona, Spain
May 19-20, 2019
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Sunday, May 19 • 17:45 - 17:50
Nobody Knows What PGs are Good For, Only I Do - Danil Kipnis, 1&1 IONOS GmbH

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While being a member of a team developing a distributed low-latency block-store, the author has been asked the question "why not just use ceph?" so often that he finally forced himself to understand some of the crush/rados basics.

It turned out, the block-store his team was working on was fully "declustered", while the ceph PG-indirection layer allowed to limit the level of "declustering".

PG concept is explained in various online sources but rather from a ceph configuration perspective. In this short talk, it is shown from a developer perspective on a very small example cluster what particular technical problem PG layer solves and how. Specifically, we illustrate the trade-off between cluster utilization during failure recovery and data loss probability due to coincident device failures and show how exactly PGs allow to favor the former or the latter.


Danil Kipnis

Linux Kernel Developer, 1&1 IONOS Cloud GmbH
Danil Kipnis is a Linux kernel developer at 1&1 IONOS Cloud (former Profitbricks GmbH). He works in the storage team designing and developing components for in-house SDS solution centered around a low latency RDMA network. He holds a Master's degree in Computer Science from TU-Berlin... Read More →

Sunday May 19, 2019 17:45 - 17:50 BST