On Mon, Jul 4, 2011 at 10:21 AM, Paul Loy <ketera...@gmail.com> wrote:
> Well, by issuing a nodetool move when a node is under high load, you > basically make that node unresponsive. That's fine, but a nodetool move on > one node also means that that node's replica data needs to move around the > ring and possibly some replica data from the next (or previous) node in the > ring. So how does this affect other nodes wrt RF and quorum? Will quorum > fail until the replicas have moved also? > > On Mon, Jul 4, 2011 at 3:08 PM, Dan Hendry <dan.hendry.j...@gmail.com>wrote: > >> Moving nodes does not result in downtime provide you use proper >> replication factors and read/write consistencies. The typical recommendation >> is RF=3 and QUORUM reads/writes.**** >> >> ** ** >> >> Dan**** >> >> ** ** >> >> *From:* Paul Loy [mailto:ketera...@gmail.com] >> *Sent:* July-04-11 5:59 >> *To:* user@cassandra.apache.org >> *Subject:* Re: How to scale Cassandra?**** >> >> ** ** >> >> That's basically how I understand it. >> >> However, I think it gets better with larger clusters as the proportion of >> the ring you move around at any time is much lower.**** >> >> On Mon, Jul 4, 2011 at 10:54 AM, Subscriber <subscri...@zfabrik.de> >> wrote:**** >> >> Hi there, >> >> I read a lot of Cassandra's high scalability feature: allowing seamless >> addition of nodes, no downtime etc. >> But I wonder how one will do this in practice in an operational system. >> >> In the system we're going to implement we're expecting a huge number of >> writes with uniformly distributed keys >> (the keys are given and cannot be generated). That means using >> RandomPartitioner will (more or less) result in >> the same work-load per node as any other OrderPreservePartitioner - right? >> >> But how do you scale a (more or less) balanced Cassandra cluster? I think >> that in the end >> you always have to double the number of nodes (adding just a handful of >> nodes disburdens only the split regions, the >> work-load of untouched regions will grow with unchanged speed). >> >> This seems to be ok for small clusters. But what do you do with when you >> have several 100s of nodes in your cluster? >> It seems to me that a balanced cluster is a bless for performance but a >> curse for scalability... >> >> What are the alternatives? One could re-distribute the token ranges, but >> this would cause >> downtimes (AFAIK); not an option! >> >> Is there anything that I didn't understand or do I miss something else? Is >> the only left strategy to make sure that >> the cluster grows unbalanced so one can add nodes to the hotspots? However >> in this case you have to make sure >> that this strategy is lasting. Could be too optimistic... >> >> Best Regards >> Udo**** >> >> >> >> >> -- >> --------------------------------------------- >> Paul Loy >> p...@keteracel.com >> http://uk.linkedin.com/in/paulloy**** >> >> No virus found in this incoming message. >> Checked by AVG - www.avg.com >> Version: 9.0.901 / Virus Database: 271.1.1/3743 - Release Date: 07/04/11 >> 02:35:00**** >> > > > > -- > --------------------------------------------- > Paul Loy > p...@keteracel.com > http://uk.linkedin.com/in/paulloy > No. If you are using nodetool move (or any of the nodetool operations) quorum and replication factor is properly maintained.
