[LUDOC-442] Documentation needed for LU-11213 DNE work

• Status: Resolved
• Project: Lustre Documentation
• Fix Version/s: Lustre 2.13.0 Manual
• Type: New Feature
• Priority: Blocker
• Reporter: Joseph Gmitter (Inactive)
• Assignee: Lai Siyao
• Resolution: Fixed

Description

Documentation needed for LU-11213 DNE work

Issue Links

• has to be finished together with: LU-11213 DNE3: remote mkdir() in ROOT/ by default

Comments

[Joseph Gmitter (Inactive)]

Lai once stated the following, which needs to be expanded upon for the manual:

A new hash type "space" is added to balance MDT space usage, once a default directory stripe is set on a plain directory, e.g.
lfs setdirstripe -D -i -1 -H space <dir1>

The subsequent syscall "mkdir" (NB, not "lfs mkdir ...") under <dir1> will choose a MDT with balanced space usage, the policy is:

• if free inodes/blocks on all MDT are almost the same, choose MDT roundrobin.
• otherwise create more subdirectories on MDTs with more free inodes/blocks.

[Joseph Gmitter (Inactive)]

laisiyao: I know we spoke about this quite some time ago, but can you look at the latest copy of the manual and suggest where exactly that we should insert the above text? Is anything more needed to add?

[Lai Siyao]

As we talked before, there doesn't exist a chapter for directory creation, so even the original interface introduced by LU-11213 is changed by LU-12624: 'space' hash type is removed, and now 'lfs setdirstripe -D -I -1' will produce the same effect, that means, if the starting MDT offset is '-1', the directory will be created by MDT space/inode usage.

Note that the patch for LU-12624 https://review.whamcloud.com/#/c/35825/ is not landed yet.

[Joseph Gmitter (Inactive)]

OK, so you are proposing that we create a new section/chapter this and include the changes in LU-12624 for that work. What area of the manual should we insert this section?

[Lai Siyao]

Maybe not in a new section, we can add this in section "13.10. Creating a directory striped across multiple MDTs", explain the effect of argument '-mdt-index' and '-mdt-hash' of command 'lfs setdirstripe', and also explain default directory layout here.

[Gerrit Updater]

Joseph Gmitter ([e-mail]) uploaded a new patch: https://review.whamcloud.com/36615
Subject: LUDOC-442 dne: directory creation by space/inode
Project: doc/manual
Branch: master
Current Patch Set: 1
Commit: f15a832c2ea297df514ff54326fcfcd03237c33e

[Gerrit Updater]

Joseph Gmitter ([e-mail]) merged in patch https://review.whamcloud.com/36615/
Subject: LUDOC-442 dne: directory creation by space/inode
Project: doc/manual
Branch: master
Current Patch Set:
Commit: ccce8bbf109d3531df7ae5b6c65af04e9b48a757