Am 07.04.2014 13:24, schrieb Hari Rajendhran:
1) I am confused why cassandra uses the entire disk space ( / Directory) even when we specify /var/lib/cassandra/data as the directory in Cassandra.yaml file
2) Is it only during compaction ,cassandra will use the entire Disk space ?
3) What is the best way to monitor the cassandra Disk usage ?? is there a opensource monitoring tool for this ??


if your / and /var/lib/cassandra/data are on different disks (or partitions) only /var/lib/cassandra/data will get filled entirely. Often this is not the case per default and you will have to create this mountpoints by yourself. Also keep in mind to keep commitlogs on a seperate disk from data to improve performance.

The extra space is only needed during compaction - but cassandra will fire up compactions by itself, so you must keep this free space maintained all the time. This is valid for SizeTieredCompation, Leveled- or HybridCompations are "cheaper" on disk space.

For the last point - there are many tools to monitor your servers inside your cluster. Nagios, Hyperic HQ and OpenNMS are some of them - you can define alerts which keep you up to date.