[lustre-discuss] tune2fs being blocked by MMP

[Mohr Jr, Richard Frank (Rick Mohr)]

> On Aug 4, 2016, at 9:39 AM, Gibbins, Faye <Faye.Gibbins at cirrus.com> wrote:
> 
> Yes it is mounted. But that's not always a problem. We have a test lustre cluster where it's mounted and the tune2fs works fine. But it fails in production.
> 
> Production have failover turned on for the OSTs. Something absent on that particular test cluster.
> 
> Is it possible there's something in lustre that prohibits tune2fs working only when failover is on for an OST?

For failover, MMP (multi-mount protection) is enabled.  I don’t know all the low-level details, but the server that has the OST mounted writes a bit of info to the disk periodically to indicate that it is in use.  If another host tries to mount the OST, it looks at the MMP info.  If it is recent, it assumes the OST is in use and won’t mount it.  I suspect that tune2fs is doing something similar.

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