Multiple data nodes with different storage size

Elastic Stack Elasticsearch
1

Hi,

I will reach soon my maximum cluster data size.

I would like to add a temporary data node until I received a new one.

This node has less storage than others but I wonder what will happened if I add it into my cluster.

I have 4 data nodes with 25Tb each and I want to add little one with 20To.

Do my cluster will blocked because of data threshold limitation ?

Best regards,

Thomas R.

2

When you add the node, the cluster will start to rebalance shards into it and fill it up as it goes by shard count, not disk size, and assumes all nodes are the same size (less than ideal, IMO).

When THAT node fills up, it won't allocate more shards to it but it'll all run normally, and add data, etc. Unless it totally runs out of space, then the affected indexes will go read only and you may have to move some shards.

Plus given the new one is 20T vs. the existing 25T, likely you won't fill up anyway, depending how full you are already.

Anyway, just add it and should be fine but keep an eye on it. It will fill slowly as it only moves two shards at a time and moving 20TB of data might take a while. As it gets close to the lower watermark (I think 85%), watch its behavior; it'll stop adding new shards, but existing shards can grow, though given shards should be <50GB or so, you'd need a lot to grow a lot to eat up your final 15%/3TB.

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3

Hi,

May be you can temporarily disable auto-rebalance by setting
"cluster.routing.rebalance.enable" to "none"

And manually rebalance some indices with the /_cluster/reroute API

Dominique

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