[OmniOS-discuss] r151014 users - beware of illumos 6214 - steps to check and repair...

[Paul B. Henson]

> From: Guenther Alka
> Sent: Monday, September 14, 2015 9:21 AM
> 
> 1. what is the recommended way to detect possible problems
>    a. run scrub? seems useless

I don't think it is necessarily useless, it might detect a problem. However,
from what I understand there might be a problem it doesn't detect. So it can
be considered verification there is a problem, but not verification that
there isn't.

>    b. run zdb pool and check for what

I ran a basic zdb and also a 'zdb -bbccsv', the former seems to be core
dumping on parsing the history, but the latter ran successfully with no
issues. If I understood George correctly, 'zdb -bbccsv' should be fairly
reliable on finding metadata corruption as it traverses all of the blocks.

> 2. when using an L2Arc and there is no obvious error detected by scrub
> or zdb
>    a. trash the pool and restore from backup  via rsync with possible
> file corruptions but ZFS structure is 100% ok then
>    b. keep the pool and hope that there is no metadata corruption?
>    c. some action to verify that at least the pool is ok: ....

Hmm, at this point given a successful scrub and successful zdb runs I'm
going to keep my fingers crossed that I have no corruption. I was only
running the buggy code for it out of month, without a particularly high
load, so hopefully I got lucky.

> 3. when using an L2Arc and there is an error detected by scrub or zdb
[...]
>    b. keep the pool and hope that there is no metadata corruption

If the scrub or zdb detect errors, it is possible your box might panic at
some point, or be unable to import the pool after a reboot. So in that case,
I don't think just keeping it is advisable :). I'm not sure if there is any
way to fix it or if the best case is to try to restore it or temporarily
transfer the data elsewhere, re-create it, and put it back.