💡 This feature is disabled by default in release
Ondat compression is handled on a per volume basis and is disabled in
v2.2.0, as performance is generally increased when compression is disabled due to block alignment.
- This means that there is a trade off between volume performance and the space the volume occupies on the backend device.
Ondat detects whether a block can be compressed or not by creating a heuristic that predicts the size of a compressed block.
- If the heuristic indicates that the compressed block is likely to be larger than the original block then the uncompressed block is stored.
- Block size increases post-compression if the compression dictionary is added to a block that cannot be compressed. By verifying whether blocks can be compressed, disk efficiency is increased and CPU resources are not wasted on attempts to compress incompressible blocks.
- Ondat’s patented on-disk format is used to tell whether individual blocks are compressed without overhead. As such volume compression can be dynamically enabled/disabled even while a volume is in use.
How To Enable Ondat Compression?
Compression can be enabled by setting the Ondat Feature Label »
storageos.com/nocompress=false on a volume at volume creation time.
- For more information on how to enable compression, review the Data Compression operations page.
Ondat Compression & Data Encryption
When Ondat compression and data encryption are both enabled for a volume, blocks are compressed first and then encrypted.