Elasticsearch multi path and RAID-0

(Svarup) #1

ElasticSearch give one option to add multiple data path so my question is, is it beneficial to give multiple path that are configured in RAID-0

Ex: path.data: /mnt/md0, /mnt/md1 are the path we use in elasticsearch.yml and those two path are configured in RAID-0

(Jymit Singh Khondhu) #2

Multiple paths in path.data stripes your shards across the paths (at the shard level).
Using RAID 0 stripes your shards across the disks (at the block level).

In the first case if you lose a disk, you lose the shards on that disk and nothing else.
In the second case, if you lose a disk, you lose all of your shards on that machine. Therefore the first gives you increased safety, but the trade off is lower performance.

(Svarup) #3

As you said in the second case, if you lose a disk, you lose all of your shards on that machine. but what if i have replica on other machine with same configuration.

is elasticsearch balance primary and replica shard on this case?

(Jymit Singh Khondhu) #4

Please explain this setup more?

(Svarup) #5

let say i have 2 node with radi-0 configuration and multiple path set as i said above

node1-path.data: /mnt/md0, /mnt/md1

node-2-path.data: /mnt/md2, /mnt/md3

as you said if any disk on your first node failed then all shards will no longer usable because of RAID-0 configuration i agree on this but i have second node so does elasticsearch balnce the primary shards that are failed in node1 to node2 for fully functional cluster?

(Jymit Singh Khondhu) #6

You will have primary and replica shards balanced in all paths. Even if you lose node1-path.data: /mnt/md0, /mnt/md1 That would have contained primary and replica shards, thus loss of data.

By default, Elasticsearch will not allocate the same index's primaries and replicas on the same node.

(system) #7

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