Add a tool to change a volume's replication setting.

[seaweedfs]

Add a tool to change a volume's replication setting.

[chrislusf]

Added a tool, "change_replication", in the "unmaintained" section. It can be used to view or change a volume's replication setting.

[chrislusf]

1. The volumes are replicated.
2. Could be a feature later. Now this is not possible. Theoretically you just need to write some code to change the replication type in the volume's super block, and make a copy of the volume. But there are no tools/interface/api to do this yet.
3. Shutdown servers. Move volume 1 from B to C. Restart the servers.

[fedotxxl]

Theoretically you just need to write some code to change the replication type in the volume's super block Can you provide sample? I think adding one more replica is pretty common task

[chrislusf]

The file go/storage/volume_super_block.go has related code.

The superblock is a 8 bytes block just for meta data about the volume. The second byte is the replica placement byte. If you need to add one more replica, basically you can change this specific byte.

/*

• Super block currently has 8 bytes allocated for each volume.
• Byte 0: version, 1 or 2
• Byte 1: Replica Placement strategy, 000, 001, 002, 010, etc
• Byte 2 and byte 3: Time to live. See TTL for definition
• Rest bytes: Reserved
  */
  type SuperBlock struct {
  version Version
  ReplicaPlacement *ReplicaPlacement
  Ttl *TTL
  }

[chrislusf]

Need to add a tool to change a volume's replication setting.

[yanyiwu]

2. Could be a feature later. Now this is not possible. Theoretically you just need to write some code to change the replication type in the volume's super block, and make a copy of the volume.

This feature is strong demand. I am waiting for it too.

[atrniv]

+1

[atrniv]

Is there any way to do this manually for now ? I need to do this for a migration of some production servers to a new cluster.

[wu0407]

+1

[mosic]

@chrislusf Can you give an update on this feature, is it on the roadmap?

If I understood it correctly, the way it is now I would need to know in advance what kind of replication I want to use, and if I wanted to change it later (e.g. from 100 to 200) I'm out of luck. Is that right?