Dear DOJO,
This is an interesting question related to a DataMiner cluster of 7 DMAs running version 10.1. When full DataMiner backups are executed, one would expect the Cassandra DB disk size to be similar to the size of the DataMiner Full Backup file. Example below is for a DMA with this expected behavior (DMA1):
We are seeing a different behavior in two DMAs of this same cluster. See screenshot below for DMA 5:
As you can see, this DMA 5 backup was completed with no errors with 50% of the size of the Cassandra DB. There are other DMAs for which the backup is 25%~30% of the Cassandra DB.
How can this size difference be explained?
As a follow-up question, we'd also like to know if there is a way to query a Cassandra DB to find the list of elements that takes more space in the DB. We know the amount of KPIs stored for historical alarm and trending purposes are really the heavy contributors of this DB disk size.
Thanks!
Have you verified that the drive where the backup is written to has sufficient disk space? You can check the trending for 'free disk space' (available in Microsoft element of the affected DMA) around the time the backup completed. The Backup log file will indicate if there were any issues that prevented the backup from executing( e.g. snapshots, disk) and might refer the user to the SLCassandraBackup log which contains detailed errors.