On Mar 20, 2010, at 2:53 AM, Lenin Gali wrote: > 1. Eventual consistency: Given a volume of 5K writes / sec and roughly 1500 > writes are Updates per sec while the rest are inserts, what kind of latency > can be expected in eventual consistency?
Depending on the size of the cluster you're not looking at much latency at all. On the order of 10's of ms's. > 2. Performance: Are there any bench marks on how many writes /sec and > reads/sec cassandra supports on an "n node" cluster? a Node can be of > variable size and would like to know the hardware/software details of the > cluster as well. Cassandra's performance is impressive. We had one node spike at 103,000 reads a second with a load of only about 6, which is high, but not alarmingly so. > 3. EC2: Has any one implemented cassandra on EC2 and what kind transaction > volume are they using it for and how is their experience with cassandra on > EC2?. We have a 15 node cluster on EC2. We have a patch that is a rack aware strategy specifically for EC2 zones where it replicates keys in a manner so that you have one key in each AZ. We run Cassandra across 3 AZ's on large instances with the ephemeral drives in a RAID0 setup with XFS. You might also be interested in this: http://stu.mp/2009/12/disk-io-and-throughput-benchmarks-on-amazons-ec2.html > 4. Overhead and issues: What are typical nightmare scenario's one could face > when using Cassandra for heavy write / read intensive systems? We haven't ran into any, but when we do find hot spots in the cluster we bootstrap a new node into the cluster with a token range that will alleviate the hot spot. This is rather painless in our experiences. > 5. Backups : If there is a 4 or 5 TB cassandra cluster what do you recommend > the backup scenario's could be? There isn't one that I know of. This is what the replication factor is for. We keep three copies of each key in three different datacenters. That's our backup strategy. > Also, Does cassandra support counters? Not yet, but there's active work happening in this area. > Digg's article said they are going to contribute their work to open source > any idea when that would be? Chris Goffinet is a committer to Cassandra. Digg's contributions are contributed back in an almost daily fashion. --Joe
