rear backup process takes too long with many disks

Solution Verified - Updated -

Environment

  • Red Hat Enterprise Linux (RHEL) 6,7
  • rear-1.17.2
  • rear-2.00
  • rear-2.4.2

Issue

When a system has many multipath devices (~500 disks and paths), creating the ReaR rescue takes several hours.

Resolution

Root Cause

Previously, ReaR employed several time consuming or redundant calls:

  • the get_device_name() function to scan all multipath devices multiple times without caching the information (legacy code, when kernel has no /sys/block/<dev>/dm/name node)
  • the get_device_name() function to scan the multipath devices even if the results were not used
  • the collect of unused /sys/class/fc_transport information

After optimizations implemented, the ReaR rescue takes several minutes only.

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