Okay. So what happens when I try to add a third DC? Since we would be using RAS any new node would get the entire dataset.
On Jul 28, 2011, at 5:49, Jonathan Ellis <jbel...@gmail.com> wrote: > The steps are the same for RUS -> RAS no matter what version of > Cassandra you are on, but 0.7 introduced NTS which is designed to make > adding datacenters easier. > > On Thu, Jul 28, 2011 at 6:57 AM, Ashley Martens <amart...@ngmoco.com> wrote: >> Thank you. For 0.7 are the steps similar? >> >> >> >> On Jul 27, 2011, at 19:56, Jonathan Ellis <jbel...@gmail.com> wrote: >> >>> As you know, with 0.6 adding a datacenter is not as easy as 0.7 with >>> NetworkTopologyStrategy. With 0.6 there is a right way that will work >>> with some manual effort, and a wrong way that can cause you major pain >>> and grief. >>> >>> The right way: >>> - Switch to a DC-aware snitch but leave your cluster on RUS to start with. >>> - Bootstrap the 2nd datacenter nodes (halfway) in between your 1st >>> datacenter tokens, so your ring alternates DC1 DC2 DC1 DC2 etc. Do >>> this one at a time for minimum disruption. You should have equal node >>> counts in each DC because RAS will keep data in each DC about equal. >>> - Switch the cluster to RAS >>> - Start repair. You will need to run repair on each node. In 0.6 you >>> should only run repair against one node at a time. >>> - While repair is going on, you need to do reads at at least CL.QUORUM >>> or data may appear to be missing, since it's not yet in all the places >>> the new strategy will look. (But by alternating DC around the ring, 2 >>> of the 3 replicas are guaranteed to be the same for both RUS and RAS.) >>> >>> The wrong way: >>> - Switch to RAS, then start adding nodes in the new DC. As soon as >>> you add the first node in DC2, RAS will try to replicate ALL the rows >>> in DC1 to it. Usually this overwhelms the DC2 node and it dies a >>> fiery death. >>> >>> On Wed, Jul 27, 2011 at 7:44 PM, Ashley Martens <amart...@ngmoco.com> wrote: >>>> I have a current 0.6.x cluster in a single datacenter with RackUnaware and >>>> am looking to expand into a second data center. I know I need to change to >>>> RackAwareStrategy however, I'm not sure what will happen to my data when I >>>> restart the nodes in the current cluster before I even add the new DC. Will >>>> the data need to move based on the rack each node is in or will it stay on >>>> the node it is currently on? Also, when I start adding nodes in the new DC >>>> to the cluster should they come in one at a time, like bootstrap, or should >>>> I light up several at the same time to distribute the data? >>>> >>>> For reference I have 19 nodes in my cluster. >>>> >>>> Thanks. >>>> >>> >>> >>> >>> -- >>> Jonathan Ellis >>> Project Chair, Apache Cassandra >>> co-founder of DataStax, the source for professional Cassandra support >>> http://www.datastax.com >> > > > > -- > Jonathan Ellis > Project Chair, Apache Cassandra > co-founder of DataStax, the source for professional Cassandra support > http://www.datastax.com
