the thing that will help most in 0.5 is to increase your KeysCachedFraction to 0.2 or even more, depending on your workload.
On Sat, Jan 30, 2010 at 5:23 AM, Suhail Doshi <digitalwarf...@gmail.com> wrote: > An issue I've been seeing is it's really hard to scale Cassandra with reads. > I've run top, vmstat, iostat. vmstat shows no swapping but iostat shows > heavy saturation of %util and await times over 90ms with max rMB/s of 7-8. > > I have over 7G of memory dedicated across two nodes. I am wondering what the > issue might be and how to solve this? I felt like 7 G would be enough. > > Suhail > > On Thu, Jan 28, 2010 at 7:32 PM, Ray Slakinski <r...@mahalo.com> wrote: > >> Cassandra auto shards, so you just need to point at your cluster and >> cassandra does the rest. You should read up on different partitioners though >> before you go live in production, because its not too easy to switch once >> you make that decision. >> >> http://wiki.apache.org/cassandra/StorageConfiguration#Partitioner >> >> Ray Slakinski >> On 2010-01-28, at 7:29 PM, Suhail Doshi wrote: >> >> > Another piece I am interested in is how cassandra distributes the data >> > automatically. In MySQL you need to shard and you'd pick the shard to >> > request info from--how does that translate in cassandra? >> > >> > On Thu, Jan 28, 2010 at 7:23 PM, Suhail Doshi <suh...@mixpanel.com> >> wrote: >> > >> >> We've started to use Cassandra in production and just have one node >> right >> >> now. Here's one of our ColumnFamilys: >> >> >> >> 16G Jan 28 22:28 SomeIndex-5467-Index.db >> >> 196M Jan 28 22:32 SomeIndex-5487-Index.db >> >> >> >> The first bottle neck you encounter is reads--writes are extremely fast >> even with one node. >> >> >> >> My question is, is the size of the *-Index.db files the amount of RAM >> you need available for Cassandra to do reads fast? >> >> >> >> What are some configuration options you would need to tweak besides the >> JVM's max memory size being larger. Is there any default configurations >> commonly missed? >> >> >> >> Next, if you provision more nodes will Cassandra distribute the data in >> memory so I don't need a single 16 GB node? Is there anything I need to >> build in my application logic to make this work correctly. Ideally, if I had >> a 16 GB index, I'd want it spread across 4 4GB nodes. Can any client connect >> to any one node request info and it will get the info back from a node that >> has that part of the index in memory? >> >> >> >> What's the best way to do efficient reads? >> >> >> >> Suhail >> >> >> >> >> >> > > > -- > http://mixpanel.com > Blog: http://blog.mixpanel.com >
