[Lustre-discuss] targets start order in Lustre 2.4.3

[White, Cliff]

In a failover situation, any target can be stopped and restarted without
  impact on other nodes. The startup order in the manual is for a cold
startup/full shutdown situation, and does not apply to a running
filesystem and failover.

You should not have the ordering directive, I think. In particular, the
MGT is only used for client/server mounts, if the filesystem is up and
running the MGT failover should be very transparent to the rest of the
cluster and should never require another node to be restarted.

Cliffw


On 5/23/14, 7:58 AM, "Riccardo Murri" <riccardo.murri at uzh.ch> wrote:

>Hello,
>
>The online Lustre manual recommends that Lustre targets are started in
>this order[1]: MGT, MDT, OSTs, clients.
>
>[1]: 
>http://build.whamcloud.com/job/lustre-manual/lastSuccessfulBuild/artifact/
>lustre_manual.xhtml#dbdoclet.50438194_24122
>
>Now we are setting up an HA cluster with Pacemaker, and a strict
>ordering directive ("order ... Mandatory: ostXX mdt mgt") results in a
>complete restart of all targets if the MGT is migrated. In my
>experience (with Lustre 1.8.5) this is most of the time unnecessary,
>and Lustre can recover from a single target restart.  However, we have
>recently switched to Lustre 2.4.3 and things might have changed.
>
>So the question is: is this order strict (in Lustre 2.4.3), or can a
>target be stopped and restarted on another node without affecting the
>targets running on other nodes?
>
>Thanks for any help!
>
>Riccardo
>
>--
>Riccardo Murri
>http://www.gc3.uzh.ch/people/rm
>
>Grid Computing Competence Centre
>University of Zurich
>Winterthurerstrasse 190, CH-8057 Zürich (Switzerland)
>Tel: +41 44 635 4222
>Fax: +41 44 635 6888
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