In order to do backups and performance testing, as well as other maintenance, we want to depool codfw Swift from serving production traffic.
Date: 22th of February.
Revert: 3rd of March.
The intention is to be depooled, if no issues found, for a minimum of 7-10 days.
Depooled means we will avoid end-user reads, but writes will continue normally, mirroring eqiad state.
Because 260+ GB of images have to be downloaded in a few days, the initial backup should have an acceptable level of bandwidth, a number given has been around 5Gbps.
In order to avoid user performance impact, try to achieve this download bandwidth by querying in parallel Swift API and also using Mediawiki public API (or if not available, PHP functions that abstract the download work needed).
While directly using Swift API is likely to be more direct and performant, it would also be more complex because we would have to implement a lot of mediawiki logic ourselves- So a higher level mediawiki layer would be ideal to abstract the storage details (specially knowing it could change in the future).
Depooling a DC for swift could be a dangerous actions, so it will need careful preparation, but it may be worth to avoid user impact during the initial download time. Involve as much people as possible during the test