I am just curious about which partitioner you are using? On Thu, Nov 17, 2011 at 4:30 PM, Philippe <watche...@gmail.com> wrote:
> Hi Todd > Yes all equal hardware. Nearly no CPU usage and no memory issues. > Repairs are running in tens of minutes so i don't understand why > replication would be backed up. > > Any other ideas? > Le 17 nov. 2011 02:33, "Todd Burruss" <bburr...@expedia.com> a écrit : > > Are all of your machines equal hardware? Since those machines are sending >> data somewhere, maybe they are behind in replicating and are continuously >> catching up? >> >> Use a tool like tcpdump to find out where the data is going >> >> From: Philippe <watche...@gmail.com> >> Reply-To: "user@cassandra.apache.org" <user@cassandra.apache.org> >> Date: Tue, 15 Nov 2011 13:22:38 -0800 >> To: user <user@cassandra.apache.org> >> Subject: Re: Network traffic patterns >> >> Sorry about the previous message, I've enabled keyboard shortcuts on >> gmail...*sigh*... >> >> Hello, >> I'm trying to understand the network usage I am seeing in my cluster, can >> anyone shed some light? >> It's an RF=3, 12-node, cassandra 0.8.6 cluster. repair is performed on >> each node once a week, with a rolling schedule. >> The nodes are p13,p14,p15...p24 and are consecutive in that order on the >> ring. Each node is only a cassandra database. I am hitting the cluster from >> another server (p4). >> >> p4 is doing this with 20 threads in parallel >> >> 1. read a lot of data (some columns for hundreds to tens of thousands >> of keys, split into 512-key multigets) >> 2. process the data >> 3. write back a byte array to cassandra (average size is 400 bytes) >> 4. go back to 1 >> >> According to my munin graphs, network usage is about as follows. I am not >> surprised at the bias towards p13-p15 as p4 is getting & storing data >> mainly for keys located on one of those nodes. >> >> - p4 : 1.5Mb/s in and out >> - p13-p15 : 15Mb/s in and 80Mb/s out >> - p16-p24 : 45Mb/s in and 5Mb/s out >> >> What I don't understand is why p4 is only seeing 1.5Mb/s while I see >> 80Mb/s on p13 & p15. >> >> The way I understand this: >> >> - p4 makes a multiget to the cluster, electing to use any node in the >> cluster (IN traffic for describe the query) >> - coordinator node replays the query on all 3 replicas (so 3 servers >> each get the IN traffic, mostly p13-p15) >> - each server replies to coordinator >> - coordinator chooses matching values and sends back data to p4 >> >> So if p13-p15 are outputting 80Mb/s why am I not seeing 80Mb/s coming >> into p4 which is on the receiving end ? >> >> Thanks >> >> 2011/11/15 Philippe <watche...@gmail.com> >> >>> Hello, >>> I'm trying to understand the network usage I am seeing in my cluster, >>> can anyone shed some light? >>> It's an RF=3, 12-node, cassandra 0.8.6 cluster. The nodes are >>> p13,p14,p15...p24 and are consecutive in that order on the ring. >>> Each node is only a cassandra database. I am hitting the cluster from >>> another server (p4). >>> >>> The pattern on p4 is the pattern is to >>> >>> 1. read a lot of data (some columns for hundreds to tens of >>> thousands of keys, split into 512-key multigets) >>> 2. process the data >>> 3. write back a byte array to cassandra (average size is 400 bytes) >>> >>> >>> p4 reads as >>> >> >>
