We have the following stats on single node cassandra on Amazon EC2/Rightscale m1.Xlarge instance with 4 ephemeral disks with raid0. (15 GB Total Memory, 4 Virtual Cores, 2 ECU , Total ECU = 8)
Linux - CentOS release 5.4 (Final)
cassandra version = apache-cassandra-1.1.0
java version "1.6.0_14" Java(TM) SE Runtime Environment (build 1.6.0_14-b08) Java HotSpot(TM) 64-Bit Server VM (build 14.0-b16, mixed mode)
configs from cassandra.yaml=================
i have tried to do some experiments with GC
10 GB RAM is allocated to cassandra Heap, 3500MB is Heap NEW size.
JVM_OPTS="$JVM_OPTS -XX:+UseCMSInitiatingOccupancyOnly -XX:+UseCompressedOops"
following stats are from OpsCenter community 2.0
Read Requests 208 to 240 per second
Write Requests 18 to 28 per second
OS Load 24.5 to 25.85
Write Request Latency 127 to 160 micros
Read Request Latency 82202 to 94612 micros
OS Sent Network Traffic 44646 KB avg per second
OS Recieved Network Traffic 4338 KB avg per second
OS Disk Queue Size 13 to 15 requests
Read Requests Pending 25 to 32
OS Disk latency 48 to 56 ms
OS Disk Read Throughput 4.6 Mb per second
Disk IOPs Reads 420 per second
IOWait 80 % CPU avg
Idle 13 % CPU avg
Rowcache is disabled.
One of the column family i am only reading from is created through CLI
"create column family XColFam with column_type='Standard' and comparator = 'CompositeType(BytesType,IntegerType)';"
column family SSTable Size = 7.10 GB, SSTable Count = 2
Above column family has 59499904 no. of estimated row keys (most are utf8 literal with varying length, estimated through mx4jtools) with columns like thin in nature, with the value 0 bytes.....now
most of the rows should have very small no. of columns may be 1 to 10, so with approx 20 to 30 bytes of 1st component of column name and 2nd is of 8 bytes integer....2nd component of composite column is dynamic could repeat but probability is low.......1st component repeats in varieties but no. of columns in rows could be different.
i have tried SnappyCompression to compress the column family but there was no change in size.
I have a scheduled service that run for hours with 20 threads and make random read requests for multiple keys (for now its 2 keys per request) to this column family and read full rows, no column slice or etc.
But i think it is not performing good now......proccessing too few request per minute.............It was working better before when the column family size was not that big.....it was around 3 to 4 GB.
I am afraid read performance degrade too fast with the increase in size of the column family.
I have also tried to tweak some GC and memory stuff, because before that i was having lots GC and CPU usage.....when data size was smaller and there was very small iowait in wave form.
your suggestions will be appreciated............how can i increase the cassandra performance.