All shards of an index allocated to same node, despite space on other nodes



I am new to this community.


I have a cluster of 5 graylog nodes connected with 5 elasticsearch nodes, all with similar size disk , RAM, cpu, network.
elastricsearch is version 2.3.4.

The message traffic is about constant, around 30 GB per hour, a bit less during night.

I use 2 Index sets. default and secondary. each index uses 5 shards, and 0 replicas.

It was working well for months, but it looks like something happened few days ago.

I am checking logfiles of both elasticsearch and graylog but nothing relevant found.

The messages are still being processed and stored OK, just I noticed that one(primary) server is getting disk alarms all the time (over 90%), but other nodes have plenty of space under 70 %..

The reason for this disk alarms is that all indexes created in Secondary index set have 5 shards, but all shars are located on primary node.

Interestingly enough, the shards in the Default index are still well distributed over 5 nodes.

First I tried to set the disk allocation, but no change
cluster.routing.allocation.disk.watermark.low: "76%"
cluster.routing.allocation.disk.watermark.high: "84%"

I also tried to rotate the active write index, it created new one, but also this one had 5 shards on primary node.

I managed to manualy run commnad to move some shards to other nodes. But it is not enogh, as there are more new messages that are reallocate.

Any suggestions, what can I check or set to "force" this Secondary index set to create new indexes on different shards ?


(Mark Walkom) #2

That is how Elasticsearch does allocation, not based on disk space (at least for now).

You mean different hosts? You could use forced allocation.

But perhaps you need to look at this in a different way and reduce your shard count.
5 shards for 30GB is a bit wasteful, I'd look at doing just 2 and then using _shrink to reduce the counts for the old ones to a single primary.

(system) #3

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