I'm wondering how we can backup a cluster of 10 nodes and restore on a cluster of 6 nodes. No matter the technique used for the backup (fsync, riakmanager, ...).
Any help you can give would be greatly appreciated.
I would recommend using the riak admin control panel. i am not sure if you are simply moving to 6 new servers or removing 4 current servers.
If you are removing 4 current servers use the control panel to remove the 4 servers and let it move the data over for you. Once your data is on 4 nodes you can take backups i would recommend taking xfs snapshots or stopping riak and backing up the file system you have riak data.
You are moving to 6 new nodes I would recommend adding 6 nodes to the current cluster letting them sync up and then removing the 10 old nodes. If the new nodes have xfs or LVM that would make snapshots very easy.