[lustre-discuss] Target names changing when mounting

[Mohr Jr, Richard Frank (Rick Mohr)]

> On Jul 31, 2015, at 2:08 PM, Andrus, Brian Contractor <bdandrus at nps.edu> wrote:


> I find this very confusing..
> I created a new lustre filesystem (WORK2) by creating and MDT and a single OST.
> 
> When I first create them, the names shown for Target have different values from ‘Read precious values’ and ‘Permanent disk data’
> 
> The difference is a hyphen ‘-‘ versus a colon ‘:’

<snip>

> THEN…
> 
> If I do a tunefs.lustre --writeconf , it changes the Permanent disk data AND the e2label to use an equal ‘=’ sign:

I too discovered this (the hard way) when I was trying to do some Lustre failover testing on our level system.

> Next time I mount it changes it back to the hyphen ‘-‘

As Oleg pointed out, that character is used to identify certain states for the OST, but as far as I can remember, I never saw that behavior documented anywhere.  It took us a couple hours to finally figure out what was happening.

> So.. What the heck???

Indeed.

> Now the problem/annoyance is the fact that this changes links in /dev…
> 
> And an equal sign ‘=’ is NOT a happy character for device names…

Agreed.  We use the /dev/disk/by-label device names too, and in general this has never been an issue before.  We only noticed this odd behavior during our testing when a separate issue forced us to do multiple writeconfs and we started looking at the OST states.  IMHO, I would prefer it if this type of state information could be tracked elsewhere and not have the OST label change.  If nothing else, the current behavior should be documented.

--
Rick Mohr
Senior HPC System Administrator
National Institute for Computational Sciences
http://www.nics.tennessee.edu