[LUDOC-557] Document qos_maxage

• Type: Improvement
• Resolution: Unresolved
• Priority: Medium
• Severity: 3
• Assignee: Patrick Farrell
• Reporter: Patrick Farrell

Description

Add documentation for the qos_maxage parameter which controls how long
cached filesystem statistics remain valid before being refreshed from
OSTs/MDTs during QoS stripe allocation. Currently undocumented despite
being an important tuning parameter for balancing allocation accuracy
vs system overhead.

Adds detailed section in ManagingStripingFreeSpace.xml and reference
entry in LustreProc.xml.