Moving from CellsV1 to CellsV2 at CERN
CERN, the European Organization for Nuclear Research, is running for several years a large OpenStack Cloud that helps thousands of scientists to analyze the data from the LHC.
In 2012, early in the design phase of the CERN Cloud we decided to use Nova Cells to enable the infrastructure to scale to thousands of nodes. Now with more than 280K cores spread across 70 cells that are hosted in two data centres we were faced with the challenge to migrate to Nova Cells V2 required in the Pike release.
In this presentation, we will describe how Nova Cells allowed CERN to scale to thousands of nodes, its advantages and how we mitigate the implementation issues of Nova Cells V1. Next, we will cover how we upgraded Nova from Newton with Cells V1 to Pike with Cells V2. We will explain the steps that we followed and the issues that we faced during the upgrade. Finally, we will report our experience with Cells V2 at scale, its caveats and how we are mitigate them.
