This is basically what entity groups are about - https://issues.apache.org/jira/browse/CASSANDRA-1684
On Mon, Nov 7, 2011 at 5:26 AM, Peter Lin <wool...@gmail.com> wrote: > This feature interests me, so I thought I'd add some comments. > > Having used partition features in existing databases like DB2, Oracle > and manual partitioning, one of the biggest challenges is keeping the > partitions balanced. What I've seen with manual partitioning is that > often the partitions get unbalanced. Usually the developers take a > best guess and hope it ends up balanced. > > Some of the approaches I've used in the past were zip code, area code, > state and some kind of hash. > > So my question related deterministic sharding is this, "what rebalance > feature(s) would be useful or needed once the partitions get > unbalanced?" > > Without a decent plan for rebalancing, it often ends up being a very > painful problem to solve in production. Back when I worked mobile > apps, we saw issues with how OpenWave WAP servers partitioned the > accounts. The early versions randomly assigned a phone to a server > when it is provisioned the first time. Once the phone was associated > to that server, it was stuck on that server. If the load on that > server was heavier than the others, the only choice was to "scale up" > the hardware. > > My understanding of Cassandra's current sharding is consistent and > random. Does the new feature sit some where in-between? Are you > thinking of a pluggable API so that you can provide your own hash > algorithm for cassandra to use? > > > > On Mon, Nov 7, 2011 at 7:54 AM, Daniel Doubleday > <daniel.double...@gmx.net> wrote: >> Allow for deterministic / manual sharding of rows. >> >> Right now it seems that there is no way to force rows with different row >> keys will be stored on the same nodes in the ring. >> This is our number one reason why we get data inconsistencies when nodes >> fail. >> >> Sometimes a logical transaction requires writing rows with different row >> keys. If we could use something like this: >> >> prefix.uniquekey and let the partitioner use only the prefix the probability >> that only part of the transaction would be written could be reduced >> considerably. >> >> >> >> On Nov 1, 2011, at 11:59 PM, Jonathan Ellis wrote: >> >>> Hi all, >>> >>> Two years ago I asked for Cassandra use cases and feature requests. >>> [1] The results [2] have been extremely useful in setting and >>> prioritizing goals for Cassandra development. But with the release of >>> 1.0 we've accomplished basically everything from our original wish >>> list. [3] >>> >>> I'd love to hear from modern Cassandra users again, especially if >>> you're usually a quiet lurker. What does Cassandra do well? What are >>> your pain points? What's your feature wish list? >>> >>> As before, if you're in stealth mode or don't want to say anything in >>> public, feel free to reply to me privately and I will keep it off the >>> record. >>> >>> [1] >>> http://www.mail-archive.com/cassandra-dev@incubator.apache.org/msg01148.html >>> [2] >>> http://www.mail-archive.com/cassandra-user@incubator.apache.org/msg01446.html >>> [3] http://www.mail-archive.com/dev@cassandra.apache.org/msg01524.html >>> >>> -- >>> Jonathan Ellis >>> Project Chair, Apache Cassandra >>> co-founder of DataStax, the source for professional Cassandra support >>> http://www.datastax.com >> >> >
