[gpfsug-discuss] GPFS and both Samba and NFS

Jonathan Buzzard jonathan at buzzard.me.uk
Tue Dec 17 21:21:51 GMT 2013

On 17/12/13 03:49, Adam Wead wrote:
> Hi all,
> I've been following this discussion because I use GPFS with both NFS and
> Samba.  Although, now I'm a bit concerned because it sounds like this
> may not be an appropriate thing to do.  It seems like the issue is the
> clustered implementations of Samba and NFS, yes?  Or is this for any
> implementation?

The issue is that running a GPFS cluster with Samba/NFS etc. on top is 
not in the same league as installing Linux on a single server with some 
storage attached and configuring Samba/NFS.

The system is much more complex and there are nasty ways in which your 
data can get corrupted. To proceed for example without a functional 
clone test system would be fool hardy in the extreme.

For example in my last job I had a functional clone of the live GPFS 
systems. By functional clone that means real hardware, with similar FC 
cards, attached to the same type of storage (in this case LSI/Netapp 
Engenio based) with NSD's of the same type though fewer running the same 
OS image, same multipathing drivers, same GPFS version, same Samba/CTDB 

In addition I then had a standalone Samba server, same OS, same storage, 
etc. all the same except no GPFS and no CTDB. It was identical apart 
from the vfs_gpfs module. One of the reasons I choose to compile my own 
vfs_gpfs and insert it into pucka RHEL is that I wanted to be able to 
test issues against a known target that I could get support on.

Then for good measure a test real Windows server, because there is 
nothing like being able to rule out problems as being down to the client 
not working properly with SMB.

Finally virtual machines for building my vfs_gpfs modules. If you think 
I am being over the top, with my test platform let me assure you that 
*ALL* of it was absolutely essential for the diagnosis of problems with 
the system and the generation of fixes at one time or another.

The thing is if you don't get this without being told then running a 
GPFS/Samba/CTDB service is really not for you.

Also you need to understand what I call "GPFS and the Dark Arts" aka 
"Magic levers for Samba", what they do and why you might want them. 
There are probably only a handful of people outside IBM who understand 
those, which is why you get warnings from people inside IBM about doing 
it yourself.

So by all means do it, but make sure you have the test systems in place 
and a through understanding of all the technologies involved as you are 
going to have to do support for yourself; you cannot ring IBM or RedHat 
and say my GPFS/Samba/CTDB storage cluster is not working as you are 
well of the beaten path. Sure you can get support from IBM for GPFS 
issues provided it is entirely GPFS related, but saving from Office 2010 
on a shared drive with rich permissions is giving wacked out file 
ownership and permission issues is going to be down to you to fix.


Jonathan A. Buzzard                 Email: jonathan (at) buzzard.me.uk
Fife, United Kingdom.

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