Dell EMC Metro node 7.1 Product Guide

Logging volumes

Logging volumes keep track of blocks written:

• During an inter-cluster link outage.
• When one leg of a DR1 becomes unreachable and then recovers.

After the inter-cluster link or leg is restored, the metro node system uses the information in logging volumes to synchronize the mirrors by sending only changed blocks across the link.

Logging volumes also track changes during loss of a volume when that volume is one mirror in a distributed device.

The logging volumes on the continuing cluster experience high I/O during:

• Network outages or cluster failures

• Incremental synchronization

  When the network or cluster is restored, metro node reads the logging volume to determine what writes to synchronize to the reattached volume.

There is no I/O activity during normal operations.