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Please explain how BIND 9 uses memory to store DNS zones. Sometimes it seems to use several times the amount it needs.

  • Updated on 05 Oct 2018
  • 1 minute to read
  • Contributors 

When reloading a zone named may have multiple copies of the zone in memory at one time: the zone it is serving and the one it is loading. If reloads are ultra-fast it can have more still, e.g. ones that are transferring out, the one that it is serving, and the one that is loading.

BIND 8 destroyed the zone before loading and also killed off outgoing transfers of the zone.

The new strategy allows slaves to get copies of the new zone regardless of how often the master is loaded compared to the transfer time. The slave might skip some intermediate versions, but the transfers will complete and it will keep reasonably in sync with the master.

The new strategy also allows the master to recover from syntax and other errors in the master file as it still has an in-core copy of the old contents.

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