Disperse type

Data are chunked and dispersed on multiple nodes. There is a kind of "parity" data allowing to lost one or mode nodes ("like" RAID5 or RAID6).

Pros:

  • good capacity (perfect for HDD storage)
  • simple to setup
  • simple to maintain
  • various level of protection

Cons:

  • not all configrations possible (3, 5, 6 nodes and more)
  • limited performances on SSDs (replication is better in this case)

pictore disperse principle

Disperse 3

This is similar to RAID5: there is an algorithm that will generate a kind of parity, being able to continue to work even if 1 node is down. If you reintroduce the node, it will be "healed" automatically.

picture disperse 3

If you lose one node, your data are still here. This mode will give you 66% of your total disk space.

Disperse 5

Same than 3, like RAID5, you can lose 1 node without service interruption.

picture disperse 5

In this case, you'll be able to use up to 80% of your total storage capacity!

Disperse 6

It's very similar to RAID6. You can lose up to 2 nodes, it will continue to work in read and write.

picture disperse 6

disperse 6 with 2 nodes down

Growing a disperse XOSAN

You can grow a replicated XOSAN by adding extra disperse volumes, in other words a new disperse will be like in RAID 0 with the old one. It's a distributed-disperse type. Some examples:

  • To grow a disperse 3, you need 3 new nodes. You'll add the total capacity of each disperse to make a distributed-disperse on 2x3 dispersed nodes.
  • To grow a disperse 6, you need 6 new nodes.

growing disperse

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