Cortex ingesters are semi-stateful. A running ingester holds several hours of time series data in memory before they’re flushed to the long-term storage. When an ingester shuts down because of a rolling update or maintenance, the in-memory data must not be discarded in order to avoid any data loss. The Cortex blocks storage requires ingesters to run with a persistent disk where the TSDB WAL and blocks are stored (eg. a StatefulSet when deployed on Kubernetes). During a rolling update, the l...
