Thanks Sean! Just for the record I am currently seeing 95 MB/s RX (Receive throughput ) on my spark worker machine when I do `sudo iftop -B`
The problem with instance store on AWS is that they all are ephemeral so placing Cassandra on top doesn't make a lot of sense. so In short, AWS doesn't seem to be the right place for colocating in theory. I would still give you the benefit of doubt and colocate :) but just the numbers are not reflecting significant margins in terms of performance gains for AWS On Sat, Dec 3, 2016 at 12:56 AM, Sean Owen <so...@cloudera.com> wrote: > I'm sure he meant that this is downside to not colocating. > You are asking the right question. While networking is traditionally much > slower than disk, that changes a bit in the cloud, where attached storage > is remote too. > The disk throughput here is mostly achievable in normal workloads. However > I think you'll find it's going to be much harder to get 1Gbps out of > network transfers. That's just the speed of the local interface, and of > course the transfer speed depends on hops across the network beyond that. > Network latency is going to be higher than disk too, though that's not as > much an issue in this context. > > On Sat, Dec 3, 2016 at 8:42 AM kant kodali <kanth...@gmail.com> wrote: > >> wait, how is that a benefit? isn't that a bad thing if you are saying >> colocating leads to more latency and overall execution time is longer? >> >> On Sat, Dec 3, 2016 at 12:34 AM, vincent gromakowski < >> vincent.gromakow...@gmail.com> wrote: >> >> You get more latency on reads so overall execution time is longer >> >> Le 3 déc. 2016 7:39 AM, "kant kodali" <kanth...@gmail.com> a écrit : >> >> >> I wonder what benefits do I really I get If I colocate my spark worker >> process and Cassandra server process on each node? >> >> I understand the concept of moving compute towards the data instead of >> moving data towards computation but It sounds more like one is trying to >> optimize for network latency. >> >> Majority of my nodes (m4.xlarge) have 1Gbps = 125MB/s (Megabytes per >> second) Network throughput. >> >> and the DISK throughput for m4.xlarge is 93.75 MB/s (link below) >> >> http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/EBSOptimized.html >> >> so In this case I don't see how colocation can help even if there is one >> to one mapping from spark worker node to a colocated Cassandra node where >> say we are doing a table scan of billion rows ? >> >> Thanks! >> >> >>