Skip to main content
Enterprise applications

Capacity management

Contributors jfsinmsp
PDFs

Managing a database or other enterprise application with predictable, manageable, high performance enterprise storage requires some free space on the drives for data and metadata management. The amount of free space required depends on the type of drive used, and business processes.

Free space is defined as any space that is not used for actual data and includes unallocated space on the aggregate itself and unused space within the constituent volumes. Thin provisioning must also be considered. For example, a volume might contain a 1TB LUN of which only 50% is utilized by real data. In a thin provisioned environment, this would correctly appear to be consuming 500GB of space. However, in a fully provisioned environment, the full capacity of 1TB appears to be in use. The 500GB of unallocated space is hidden. This space is unused by actual data and should therefore be included in the calculation of total free space.

NetApp recommendations for storage systems used for enterprise applications are as follows:

SSD aggregates, including AFF systems

Tip NetApp recommends a minimum of 10% free space. This includes all unused space, including free space within the aggregate or a volume and any free space that is allocated due to the use of full provisioning but is not used by actual data. Logical space is unimportant, the question is how much actual free physical space is available for data storage.

The recommendation of 10% free space is very conservative. SSD aggregates can support workloads at even higher levels of utilization without any effect on performance. However, as the utilization of the aggregate increases, the risk of running out of space also increases if utilization is not monitored carefully. Furthermore, while running a system at 99% capacity may not incur a performance penalty, but it would likely incur management effort trying to keep it from filling up completely while additional hardware is ordered, and it may take some time to procure and install additional drives.

HDD aggregates, including Flash Pool aggregates

Tip NetApp recommends a minimum of 15% free space when spinning drives are used. This includes all unused space, including free space within the aggregate or a volume and any free space that is allocated due to the use of full provisioning but is not used by actual data. Performance will be impacted as free space approaches 10%.