[LU-7827] DNE3: automatically select MDT for lfs mkdir

• Type: Improvement
• Resolution: Duplicate
• Priority: Minor
• Affects Version/s: Lustre 2.8.0, Lustre 2.9.0
• Labels: dne3
• Assignee: WC Triage
• Reporter: Andreas Dilger

Description

Currently, lfs mkdir creating a remote directory requires specifying the MDT index at directory create time, and if -i -1 is used it does not select the "best" MDT at creation time.

Since the selection of the MDT for remote directory creates is decided by the client, it may be necessary to do a statfs of all MDTs (and cache the result for a short time) on the client to select the best MDT based on the free inodes, and some kind of round-robin if the free inodes are approximately the same (e.g. within 10% of each other).

Issue Links

• duplicates: LU-10277 DNE3: allow 'lfs mkdir' to create directory on MDS which has more space
• is related to: LU-6831 The ticket for tracking all DNE2 bugs
• is related to: LU-11213 DNE3: remote mkdir() in ROOT/ by default
• is related to: LU-9435 DNE2 - object placement QoS policy
• is related to: LU-15494 DNE3: "lfs setdirstripe -D" for specific MDTs
• is related to: LU-8616 DNE3: enhance "lfs mkdir" to select specific MDTs