The saved data
InfiniBox calculates the saved capacity on the dataset tree level. The capacity counters report on the following:
- How much capacity is allocated to the dataset (in dark blue, on the image below)
- How much capacity is allocated to the dataset descendants (in light blue, on the image below)
- How much capacity is saved, due to the compression (in grey, on the image below)
- How much free capacity is there (the sum of the grey and white lines, on the image below)
Use-cases
Introducing compression to an existing InfiniBox system
- On an existing system, prior to the introduction of the compression feature, all pools and their entities are not compressed.
- Upon upgrading to an InfiniBox software release that features compression, all existing pools and their entities remain uncompressed
- When creating a new pool and marking it as compressed, it will be compressed
- The transition of an entity from a non-compressed pool to a compressed pool is described below.
Writing into a dataset
- Raw capacity - 4 * 64KB
- Compressed capacity - 64KB
- In this use case, the 256KB were compressed to 64KB
- Used capacity (allocated by the user) - 4 * 64 = 256KB
- Allocated - 64KB
- Tree allocated - 0
- Saved capacity - 256 - 64 = 192KB
Taking two snapshots
- Used capacity (allocated by the user) - 256KB
- Allocated - 64KB
- Tree allocated - 0
- Saved capacity - 192KB
Overwriting the dataset with 256KB
- Raw capacity - 256KB
- Compressed capacity - 128KB
- In this use case, the 256KB were compressed to 128KB
- Used capacity (allocated by the user) - 256KB
- Allocated - 128KB
- Tree allocated - 64
- The overwritten blocks of one of the snapshots
- Saved capacity - 192 + 128 = 320KB
Deleting a snapshot
- Used capacity (allocated by the user) - 256KB
- Allocated - 128KB
- Tree allocated - 64
- The capacity is moved to the other snapshot
- Saved capacity - 192 + 128 = 320KB
Unmapping blocks from the volume
- Used capacity (allocated by the user) - 0
- The 256KB are no longer needed
- Allocated - 0
- Tree allocated - 64
- remaining
- Saved capacity - 256 - 64 = 192KB
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