eG Monitoring
 

Measures reported by HanaDiskUsageTest

Since the SAP HANA database resides in volatile main memory, a persistency layer in the SAP HANA database engine ensures the durability of the transactions. In the event of a failure the persistency layer ensures that the database can be restored to the most recent committed state after a restart. Transactions are either completely executed or completely un-done. To ensure durability of data changes completed in the memory of the SAP HANA server nodes, database data is written to disks. The persistency layer stores data in disk volumes, organized in pages. There are two types of volumes: DATA and LOG. The data volume contains data pages and undo log information. The log volume only records redo log information. In addition, if tracing is enabled, a TRACE volume is created, which stores trace files that aid in system troubleshooting.

To enable the SAP HANA database server to provide reliable and uninterrupted data management services, each of these disk volumes should have adequate free space. If a SAP HANA database server were to rapidly run out of disk space, and administrators had no knowledge of this anomaly until it was too late, it could result in the loss of critical data, much to the displeasure of database users. To avoid this, the space usage in each disk volume of the SAP HANA database server host should be closely monitored and administrators forewarned of space contentions. The HanaDiskUsageTest test makes this possible!

This test monitors the space usage in each disk volume of the SAP HANA server, proactively detects a potential space crunch in any volume, and promptly alerts administrators to the same, so that the disk space crisis can be averted.

The measures made by this test are as follows:

Measurement Description Measurement Unit Interpretation
totalSizeMB Indicates the total size of this disk volume. MB  
freeSizeMB Indicates the amount of space that is unused in this disk volume. MB A high value is desired for this measure.
freePercent Indicates the percent of space that is currently unused in this disk volume. Percent A consistent decrease in the value of this measure is indicative of gradual erosion of space in a disk volume. You may want to free up more space by either adding more disks or by removing unnecessary or obsolete files from the disk. This depends upon the VolumeType. For instance, in case of the DATA volume, you must not delete files from this volume manually, as it can corrupt the SAP HANA system. On the other hand, if the TRACE volume runs out of space, you can delete the trace files to make room for more trace data.
growth Indicates the rate of growth in space usage in this disk volume since the last measurement period. MB/Sec If a consistent growth is noticed in the value of this measure, it is indicative of gradual erosion of space in a disk volume. You may want to free up more space by either adding more disks or by removing unnecessary or obsolete files from the disk. This depends upon the VolumeType. For instance, in case of the DATA volume, you must not delete files from this volume manually, as it can corrupt the SAP HANA system. On the other hand, if the TRACE volume runs out of space, you can delete the trace files to make room for more trace data.