<p dir="auto">Currently if a historical tier has a replication factor of 1 (meaning only 1 copy of the data across the tier) then any particular node cannot be shut down for planned maintenance without temporarily loosing the ability to query data which was hosted there.</p>
<p dir="auto">As a user of Druid, I would like my queries to always return all the data even during planned maintenance or planned node shutdowns provided there is enough overall tier capacity to hold the data.</p>
<p dir="auto">This ask is that historical nodes are able to be put into a maintenance mode such that their nodes do not count towards the replication threshold. This allows for scaling tiers down in a more controlled manner.</p>
<p dir="auto">We occasionally have capacity issues as we scale our cluster such that a lower tier fills up, and upper tiers need to be expanded to accommodate the handoff of realtime indexing tasks while the lower tiers expand. Once this is completed and segments are flowing as expected through the tiers, the "more recent data" tiers need to be shrunk back to normal operating size.</p>
<p dir="auto">Being able to put a historical node into a state where it doesn't count towards replication would help in this.</p>