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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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