[lustre-discuss] Understanding Lustre Recovery

[Ms. Megan Larko]

Salutations!

I am trying to better understand Lustre recovery after having a hardware
problem force a recovery on the Lustre File System (LFS).

For the most part, the recovery from the hardware failure succeeded.  It
took a bit of time.
The system is a vendor appliance initially based on Lustre 2.1.0 with some
vendor patches.

I was concerned about the messages "...waking for gap in transno, VBR is
OFF...".   I learned in LU-7732 that the message concerns transaction
numbers in a replay request in which no CREATE occurs such that the
transaction number is subsequenlty removed from the replay list.  The
message was deemed inaccurate and unnecessary per LU-7732 and removed in
Lustre 2.9.0 and newer.  Thanks for the info.

What about the "VBR is OFF" part of the string?  The "Lustre Software
Release Operations Manual 2.x" Section 31.4.1 VBR Messages states of VBR
that "It cannot be disabled".   The "lctl get_param
obdfilter.*.recovery_status" on an OSS shows the line "VBR:  DISABLED" for
each OST on the OSS.  The MDS recovery_status also shows VBR: DISABLED.  I
noted while reading LU-5724 that James Simmons post of recovery_status had
VBR: DISABLED as well. It seemed from the post that the VBR status was
acceptable (Mr. Simmons question in the LU was on the IR status).

* If a LFS is not in recovery (STATUS:  COMPLETE) is VBR: DISABLED printed
because a recovery operation is not currently occuring?

Secondly, the Imperative Recovery (IR) is shown as IR: ENABLED on the MDS.
For the OSS, I see from the recovery_status output that IR is enabled, on
most--but not all--the OSTs.

* Should the OST IR value be consistent across all active OSTs in a LFS?
* Why might an OST have an IR state different from its peers?

P.S.  I really appreciate the clear write-ups in the LU pages.  They have
helped me significantly.

Cheers,
megan
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