Can I add a single node of any capacity to an existing cluster?

Support Admin

started a topic
over 8 years ago

You can always add an extra node and hit rebalance...

However: - You should never add a single node bigger than the total capacity of the other nodes (ie don't add a 96TB node to a 72TB cluster). In that case, if the new node fails, the data will be impossible to be regenerated to the other nodes.

- Best practice is to never add a node with greater capacity than spare space on the remaining nodes otherwise.

you cannot efficiently use all the capacity of the new node without many rebalancing operations

you cannot regenerate data anywhere if the new node fails

Example

a 72TB cluster (20TB usable per node, 3 nodes) is 90% full and a 96TB node (88TB usable) is added. Therefore there is 18TB on each of the 3 original nodes and the total storage is 54TB.

As a rule of thumb, after rebalancing, divide the total storage by the number of nodes. 54TB / 4 = 13.5TB per node

The new node has 74.5TB of capacity remaining, yet the total free space on all the other nodes is just 19.5TB. Therefore only 19.5TB of new objects can be added and the rest of the new node will not be usable.

RECOMMENDATIONS: 1. Adding 2 nodes avoids complications and even avoids the need to do rebalancing. Can you add 2 nodes?

2. As a rule of thumb in small systems, if adding only one node it shouldn't be more than double the size of the existing nodes.

3. If adding 3+ nodes they can be any size (since they can regenerate to each other even if they are much larger than the existing nodes)

## Support Admin

However:

- You should never add a single node bigger than the total capacity of the other nodes (ie don't add a 96TB node to a 72TB cluster).

In that case, if the new node fails, the data will be impossible to be regenerated to the other nodes.

- Best practice is to never add a node with greater capacity than spare space on the remaining nodes otherwise.

ExampleTherefore there is 18TB on each of the 3 original nodes and the total storage is 54TB.

As a rule of thumb, after rebalancing, divide the total storage by the number of nodes. 54TB / 4 = 13.5TB per node

The new node has 74.5TB of capacity remaining, yet the total free space on all the other nodes is just 19.5TB. Therefore only 19.5TB of new objects can be added and the rest of the new node will not be usable.

RECOMMENDATIONS:1. Adding 2 nodes avoids complications and even avoids the need to do rebalancing. Can you add 2 nodes?

2. As a rule of thumb in small systems, if adding only one node it shouldn't be more than double the size of the existing nodes.

3. If adding 3+ nodes they can be any size (since they can regenerate to each other even if they are much larger than the existing nodes)