Comments on Arbitrarily anything...: Comparing PNUTS, HBase and Cassandra

Getting a consistent view by reading from a quorum...

2010-05-20T01:42:19.950-07:00

Getting a consistent view by reading from a quorum is the basic principal of this architecture. And like I said earlier, thats a tradeoff between latency (governed by the number of replicas needed to be read) and consistency, which the client can make. The statement about atomicity that you pointed me to does not say this, by the way. It clearly says that if a write is acked, "eventually&

If your consistency level is Quorum then it means ...

2010-05-19T22:20:45.144-07:00

If your consistency level is Quorum then it means when you read as Quorum you will see a consistent and an atomic read which will be similar to that of the hbase.... Datacenter Quorum will provide you the ability in which you will be able to see the data consistently within a Datacenter, which makes it even better for some use cases. hope that clarifies...

Thanks for giving pointers to more detailed inform...

2010-05-19T20:56:49.427-07:00

Thanks for giving pointers to more detailed information about Cassandra.
Regarding atomic writes, from the link you have posted:

"It's correct, if understood correctly. We should probably just remove it since it's confusing as written.

What it means is, if a write for a given row is acked, eventually, all the data updated in that row will be available for

In addition @cassandra writes are atomic within a ...

2010-05-19T20:50:16.905-07:00

In addition @cassandra writes are atomic within a columnfamily (within a row)
http://stackoverflow.com/questions/2055037/cassandra-atomic-reads-writes-within-a-single-columnfamily

About consistency: i was commenting about "If you can deal with eventual consistency and want a highly available system that can span across data centers" --> take a look at DCQuorum and

AK, you might want to read wikipedia.... http://en...

2010-05-19T20:25:44.718-07:00

AK, you might want to read wikipedia.... http://en.wikipedia.org/wiki/Apache_Cassandra Facebook claims that....

Yahoo paper was little old... and we asked them to use the latest release
http://www.mail-archive.com/cassandra-user@incubator.apache.org/msg02315.html 0.5 to 0.6 there was atleast 2x performance gain.

Vijay, I havent heard of a 200 node Cassandra inst...

2010-05-18T13:47:29.224-07:00

Vijay, I havent heard of a 200 node Cassandra instance. Do you have any stats/write up/paper to back up the claim?

Yes, Cassandra and HBase are in a way converging to provide similar features.

The scan performance was compared in the Yahoo! YCSB paper. Its being presented in SoCC10.

Consistency is the client's choice and I mention that the client can trade off

Most of the comments about cassandra is incorrect,...

2010-05-18T13:30:29.929-07:00

Most of the comments about cassandra is incorrect, Consistency is a choice from the client and there is always ways to make it consistent. Datacenter replication is not specified. Facebook installation is 200 nodes and i dont see any Hbase installation that big. Scans are slow was a old story. you might really need to check out the latency and the scalability and compare with numbers... i dont