How to Decommission a vmstorage Node from a VictoriaMetrics Cluster

Problem

We need to remove a vmstorage node from VictoriaMetrics cluster gracefully. Every vmstorage node contains its own portion of data and removing the vmstorage node from the cluster creates gaps in the graph (because replication is out of scope).

Setup example

We have a VictoriaMetrics cluster with 2 vminsert, 2 vmselect and 3 vmstorage nodes. We want to gracefully remove vmstorage A from the cluster.

Solution One

1. Remove vmstorage A from the vminsert list
2. Wait for the retention period
3. Remove vmstorage A from the cluster

Note: please expect higher resource usage on the existing vmstorage nodes (vmstorage B and vmstorage C), as they now need to handle all the incoming data.

Pros: Simple implementation

Cons: You may need to wait for a long period of time

Solution Two

1. Remove vmstorage A from the vminsert list (same as in Solution One).
2. Set up a dedicated vmselect node that knows only about the vmstorage node that we want to remove (vmstorage A). We need this vmselect node for migration data from vmstorage A to other vmstorage nodes in the cluster.
3. Using vmctl native import/export reads data from vmselect for vmstorage A and writes data back to vminsert nodes. 4. This process creates duplicates.
4. Turn on deduplication on vmselect nodes.
5. Remove vmstorage A from the cluster.

Note: Please expect higher resource usage on the existing nodes (vmstorage B and vmstorage C), as they now need to handle all the incoming data.

Pros: Faster way to decommission a vmstorage node.

Cons: The process is more complex compared to solution One. The vmctl import/export process may require tuning if you migrate hundreds GB of data (or more).

Hint : downsampling reduces the amount of data in a cluster; after downsampling, the vmctl migration requires less data to transfer and less time.

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