I never said it would be frequent. That was an assumption made by Ben. I am trying to understand how to "set the dials" to ensure availability and durability ... And understand the cost when the inevitable hardware failure occurs.
Sent via BlackBerry from T-Mobile -----Original Message----- From: Jonathan Shook <jsh...@gmail.com> Date: Fri, 4 Jun 2010 20:28:33 To: <user@cassandra.apache.org> Subject: Re: Seeds, autobootstrap nodes, and replication factor If I may ask, why the need for frequent topology changes? On Fri, Jun 4, 2010 at 1:21 PM, Benjamin Black <b...@b3k.us> wrote: > On Fri, Jun 4, 2010 at 11:14 AM, Philip Stanhope <pstanh...@wimba.com> wrote: >> I guess I'm thick ... >> >> What would be the right choice? Our data demands have already been proven to >> scale beyond what RDB can handle for our purposes. We are quite pleased with >> Cassandra read/write/scale out. Just trying to understand the operational >> considerations. >> > > Cassandra supports online topology changes, but those operations are > not cheap. If you are expecting frequent addition and removal of > nodes from a ring, things will be very unstable or slow (or both). As > I already mentioned, having a large cluster (and 40 nodes qualifies > right now) with RF=number of nodes is going to make read and write > operations get more and more expensive as the cluster grows. While > you might see reasonable performance at current, small scale, it will > not be the case when the cluster gets large. > > I am not aware of anything like Cassandra (or any other Dynamo system) > that support such extensive replication and topology churn. You might > have to write it. > > > b >
