the new nodes will have 1TB of data disk, but how much data will you put on them?
A ----------------- Aaron Morton Freelance Cassandra Developer @aaronmorton http://www.thelastpickle.com On 22/09/2011, at 7:23 PM, Philippe wrote: > Hi Aaron > Thanks for the reply > > I should hhave mentionned that all current nodes are running 0.8.4. > All current and future services have 2TB disks of which i have allocated only > half. I don't expect any issues here. Should I? > > Le 22 sept. 2011 01:26, "aaron morton" <aa...@thelastpickle.com> a écrit : > > How much data is on the nodes in cluster 1 and how much disk space on > > cluster 2 ? Be aware that Cassandra 0.8 has an issue where repair can go > > crazy and use a lot of space. > > > > If you are not regularly running repair I would also repair before the move. > > > > The repair after the copy is a good idea but should technically not be > > necessary. If you can practice the move watch the repair to see if much is > > transferred (check the logs). There is always a small transfer, but if you > > see data been transferred for several minutes I would investigate. > > > > When you start a repair it will repair will the other nodes it replicates > > data with. So you only need to run it every RF nodes. Start it one one, > > watch the logs to see who it talks to and then start it on the first node > > it does not talk to. And so on. > > > > Add a snapshot before the clean (repair will also snapshot before it runs) > > > > Scrub is not needed unless you are migrating or you have file errors. > > > > If your cluster is online, consider running the clean every RFth node > > rather than all at once (e.g. 1,4, 7, 10 then 2,5,8,11). It will have less > > impact on clients. > > > > Cheers > > > > ----------------- > > Aaron Morton > > Freelance Cassandra Developer > > @aaronmorton > > http://www.thelastpickle.com > > > > On 22/09/2011, at 10:27 AM, Philippe wrote: > > > >> Hello, > >> We're currently running on a 3-node RF=3 cluster. Now that we have a > >> better grip on things, we want to replace it with a 12-node RF=3 cluster > >> of "smaller" servers. So I wonder what the best way to move the data to > >> the new cluster would be. I can afford to stop writing to the current > >> cluster for whatever time is necessary. Has anyone written up something on > >> this subject ? > >> > >> My plan is the following (nodes in cluster 1 are node1.1->1.3, nodes in > >> cluster 2 are node2.1->2.12) > >> stop writing to current cluster & drain it > >> get a snapshot on each node > >> Since it's RF=3, each node should have all the data, so assuming I set the > >> tokens correctly I would move the snapshot from node1.1 to node2.1, 2.2, > >> 2.3 and 2.4 then node1.2->node2.5,2.6,2.,2.8, etc. This is because the > >> range for node1.1 is now spread across 2.1->2.4 > >> Run repair & clean & scrub on each node (more or less in //) > >> What do you think ? > >> Thanks > >
