Advanced system alert metrics

Configure advanced system metrics for memory, CPU, and disk metrics on Linux or Mac OS X. As with any database system, Cassandra performance greatly depends on underlying systems on which it is running. Before configuring advanced system metric alerts, you should first have an understanding of the baseline performance of your hardware and the averages of these system metrics when the system is handling a typical workload.

To access Advanced System metrics, choose Advanced > System in the Add Alert dialog.

Advanced Alerts submenu

Linux memory metrics


Metric	Definition
Memory free	System memory that is not being used.
Memory used	System memory used by application processes.
Memory buffered	System memory used for caching file system metadata and tracking in-flight pages.
Memory shared	System memory that is accessible to CPUs.
Memory cached	System memory used by the OS disk cache.

Linux CPU metrics


Metric	Definition
Idle	Percentage of time the CPU is idle.
Iowait	Percentage of time the CPU is idle and there is a pending disk I/O request.
Nice	Percentage of time spent processing prioritized tasks. Niced tasks are also counted in system and user time.
Steal	Percentage of time a virtual CPU waits for a real CPU while the hypervisor services another virtual processor.
System	Percentage of time allocated to system processes.
User	Percentage of time allocated to user processes.

Linux Disk metrics


Metric	Definition
Disk usage	Percentage of disk space Cassandra uses at a given time.
Free disk space	Available disk space in GB.
Used disk space	Used disk space in GB.
Disk read throughput	Average disk throughput for read operations in megabytes per second. Exceptionally high disk throughput values may indicate I/O contention.
Disk write throughput	Average disk throughput for write operations in megabytes per second.
Disk read rate	Averaged disk speed for read operations.
Disk write rate	Averaged disk speed for write operations.
Disk latency	Average time consumed by disk seeks in milliseconds.
Disk request size	Average size in sectors of requests issued to the disk.
Disk queue size	Average number of requests queued due to disk latency.
Disk utilization	Percentage of CPU time consumed by disk I/O.

Mac OS X memory metrics


Metric	Definition
Free memory	System memory that is not being used.
Used memory	System memory that is being used by application processes.

Mac OS X CPU metrics


Metric	Definition
Idle	Percentage of time the CPU is idle.
System	Percentage of time allocated to system processes.
User	Percentage of time allocated to user processes.

Mac OS X disk metrics


Metric	Definition
Disk usage	Percentage of disk space Cassandra uses at a given time.
Free space	Available disk space in GB.
Used disk space	Used disk space in GB.
Disk throughput	Average disk throughput for read/write operations in megabytes per second. Exceptionally high disk throughput values may indicate I/O contention.