Mantle: A Programmable Metadata Load Balancer for the Ceph File System

Appeared in Supercomputer.


Migrating resources is a useful tool for balancing load in a distributed system, but it is difficult to determine when to move resources, where to move resources, and how much of them to move. We look at resource migration for file system metadata and show how CephFS's dynamic subtree partitioning approach can exploit varying degrees of locality and balance because it can partition the namespace into variable sized units. Unfortunately, the current metadata balancer is complicated and difficult to control because it struggles to address many of the general resource migration challenges inherent to the metadata management problem. To help decouple policy from mechanism, we introduce a programmable storage system that lets the designer inject custom balancing logic. We show the flexibility and transparency of this approach by replicating the strategy of a state-of-the-art metadata balancer and conclude by comparing this strategy to other custom balancers on the same system.

Publication date:
November 2015

Michael Sevilla
Carlos Maltzahn
Ike Nassi
Scott A. Brandt
Sage Weil
Greg Farnum
Sam Fineberg


Available media

Full paper text: PDF

Bibtex entry

  author       = {Michael Sevilla and Carlos Maltzahn and Ike Nassi and Scott A. Brandt and Sage Weil and Greg Farnum and Sam Fineberg},
  title        = {Mantle: A Programmable Metadata Load Balancer for the Ceph File System},
  booktitle    = {Supercomputer},
  month        = nov,
  year         = {2015},
Last modified 10 Apr 2024