I just see vnodes as a way to make the problem smaller and by making the problem smaller the overall system is more agile. Aka rather then 1 node streaming 100 gb the 4 nodes stream 25gb. Moves by hand are not so bad because the take 1/4th the time.
The most simple vnode implementation is vmware. Just make sure that 3 vm nodes consecutive nodes so not end up on the same host. This is wasteful because we have 4 jvms. I envision vnodes as Cassandra master being a shared cache,memtables, and manager for what we today consider a Cassandra instance. Makes it simple to think about. On Wednesday, March 21, 2012, Peter Schuller <peter.schul...@infidyne.com> wrote: >> Software wise it is the same deal. Each node streams off only disk 4 >> to the new node. > > I think an implication on software is that if you want to make > specific selections of partitions to move, you are effectively > incompatible with deterministically generating the mapping of > partition to responsible node. I.e., it probably means the vnode > information must be kept as state. It is probably difficult to > reconcile with balancing solutions like consistent hashing/crush/etc. > > -- > / Peter Schuller (@scode, http://worldmodscode.wordpress.com) >
