2013/5/9 Liu Yuan <namei.unix at gmail.com>: > Since we don't change weight by plugging/unplugging disks, there is no > way to rebalance data. If we allow weight-change for plug/unplug, we > have to pay price: plug/unplug one disk will trigger the whole cluster > recovery. Looking at it from the other side: my node uses two disks: 2T + 500G. What happens then if I unplug the 2T disk now? It contains lot's of data. Data can't be distributed across the node disk. It's has to trigger a cluster recover. When I plug the disk backup, this node is not going to be used much. root at sheepdog001:~# collie node md info Id Size Use Path 0 1.2 TB 593 GB /mnt/ST2000DM001-1CH164_W1E2N5G6/obj 1 212 GB 253 GB /mnt/wd_WMAYP0904279 I do not like the idea of having more sheeps on a single node. I think it's dangerous because n sheeps on a node may be bigger than n copies. I the whole host dies, more nodes are going to die. That's why I like md approach. I think a recovery/rebalance is needed. Maybe not automatically, but by a collie command, so we can choose to trigger the cluster when it's less loaded. |