Given the growth rate of Wikidata, we need to increase storage capacity for WDQS.
There are 2 possible strategies:
- increase the storage capacity of our current servers
This is fairly straightforward, but would require adding storage in our current servers.
- migrate from RAID1 to RAID0
Other services (elasticsearch / cassandra) manage redundancy at the cluster level and not at the server level. For this to make sense, we need to ensure that loosing a full server is a non event (the cluster is robust to loosing a node AND reimaging is cheap). In the case of WDQS, we currently have 3 nodes per clusters (4 clusters: public / internal for both eqiad and codfw), increasing it to 4 nodes would provide enough redundancy at the cluster level that loosing a node is a non issue.
Note that while the storage ('/srv') is migrated to RAID0, we'll keep the OS on RAID1.