Hi David, Answers in line:
On 7/6/09 4:45 AM, "David Graf" <david.g...@28msec.com> wrote: > Hello > > I wanna set up a zookeeper ensemble on amazon's ec2 service. In my > system, zookeeper is used to run a locking service and to generate > unique id's. Currently, for testing purposes, I am only running one > instance. Now, I need to set up an ensemble to protect my system > against crashes. > The ec2 services has some differences to a normal server farm. E.g. > the data saved on the file system of an ec2 instance is lost if the > instance crashes. In the documentation of zookeeper, I have read that > zookeeper saves snapshots of the in-memory data in the file system. Is > that needed for recovery? Logically, it would be much easier for me if > this is not the case. Yes, zookeeper keeps persistent state on disk. This is used for recovery and correctness of zookeeper. > Additionally, ec2 brings the advantage that serves can be switch on > and off dynamically dependent on the load, traffic, etc. Can this > advantage be utilized for a zookeeper ensemble? Is it possible to add > a zookeeper server dynamically to an ensemble? E.g. dependent on the > in-memory load? It is not yet possible to add servers dynamically. There is work going on to to that on http://issues.apache.org/jira/browse/ZOOKEEPER-107. This should get into the next release (am hoping). For now, you will have to do a rolling restart if you do not want the services to do down or else restart all the machines at the same time (the zookeeper cleints should be able to handle a minor downtime of zookeeper service). Thanks mahadev > > David
