Previously, see T13076. Several Phacility issues are ripe for resolution via mass-migration:
- Balancing and compaction issues.
- Some shards are heavily loaded.
- Free instances can be put in shard jail.
- Instance types: everything is "m3.large" and a bunch of hosts have 1K+ days of uptime. The newer "m4.large" chassis is more or less a strict upgrade.
- System version: current systems are on Ubuntu 14 + PHP 5.x. We can upgrade to Ubuntu 20 + PHP 7.4.