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Is It Necessary to Set the Volume Compression Group Size to 8K When Using ODX (Offload Data Transfer)?

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Applies to

  • ONTAP 9
  • ODX (Offload Data Transfer)

Answer

  • As part of ODX requirements, when using a compressed volume, the compression format needs to be adaptive.
  • The supported compression group size is only 8K.
  • In FAS systems:
    • only post-process is permitted, and the application-io-size parameter is set to 'not allowed'.
    • Hence, there will be no background recompression and it will remain as adaptive/8K.
  • For AFF systems:
    • when the application-io-size parameter is set to 'auto', hot data gets compressed inline using 8K compression groups.
    • Cold data is then recompressed in the background using a more aggressive 32K compression group.
    • Therefore, when using ODX in an AFF environment, it is necessary to explicitly set it to 8K, not 'auto'.
    • Note:
      • The requirement to configure 8K compression group size when using CIFS ODX Offload Data Transfer applies only to platforms where Temperature Sensitive Storage Efficiency (TSSE) is supported and enabled.
      • Platforms where this KB requirement applies
        • Traditional AFF platforms where TSSE is supported
        • Environments where background recompression to 32K can occur due to TSSE behavior
        • In these environments, configuring the volume to maintain an effective 8K compression is necessary to ensure correct CIFS ODX operation.
      • Platforms where this KB requirement does NOT apply

Additional Information

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