On Wed, May 16, 2012 at 12:59 PM, Yiming Sun <yiming....@gmail.com> wrote: > Hello, > > I asked the question as a follow-up under a different thread, so I figure I > should ask here instead in case the other one gets buried, and besides, I > have a little more information. > > "We find the lack of performance disturbing" as we are only able to get > about 3-4MB/sec read performance out of Cassandra. > > We are using cassandra as the backend for an IR repository of digital texts. > It is a read-mostly repository with occasional writes. Each row represents > a book volume, and each column of a row represents a page of the volume. > Granted the data size is small -- the average size of a column text is > 2-3KB, and each row has about 250 columns (varies quite a bit from one > volume to another). > > Currently we are running a 3-node cluster, and will soon be upgraded to a > 6-node setup. Each node is a VM with 4 cores and 16GB of memory. All VMs > use SAN as disk storage. > > To retrieve a volume, a slice query is used via Hector that specifies the > row key (the volume), and a list of column keys (pages), and the consistency > level is set to ONE. It is typical to retrieve multiple volumes per > request. > > The read rate that I have been seeing is about 3-4 MB/sec, and that is > reading the raw bytes... using string serializer the rate is even lower, > about 2.2MB/sec. > > The server log shows the GC ParNew frequently gets longer than 200ms, often > in the range of 4-5seconds. But nowhere near 15 seconds (which is an > indication that JVM heap is being swapped out). > > Currently we have not added JNA. From a blog post, it seems JNA is able to > increase the performance by 13%, and we are hoping to increase the > performance by something more like 1300% (3-4 MB/sec is just disturbingly > low). And we are hesitant to disable swap entirely since one of the nodes > is running a couple other services > > Do you have any suggestions on how we may boost the performance? Thanks!
Have you tried using more threads on the client side? Generally speaking, when I need faster read/write performance I look for ways to parallelize my requests and it scales pretty much linearly. -- Aaron Turner http://synfin.net/ Twitter: @synfinatic http://tcpreplay.synfin.net/ - Pcap editing and replay tools for Unix & Windows Those who would give up essential Liberty, to purchase a little temporary Safety, deserve neither Liberty nor Safety. -- Benjamin Franklin "carpe diem quam minimum credula postero"
