[Pvfs2-users] Multiple Metadata servers on pNFS/PVFS2

[Phil Carns]

Hi Nirmal,

Are you trying to have multiple pNFS MDS servers, or multiple meta 
servers in the PVFS volume?

I don't believe that the former is supported (but I was hoping someone 
else would chime in- I have not used the pNFS/PVFS implementation first 
hand).

The latter should work fine without any particular changes to the 
installation steps except for the PVFS configuration files.

In either case I am pretty sure that the bind option to mount is not 
going to do what you are looking for.

-Phil


Nirmal Thacker wrote:
> Hello,
> 
> I have a question regarding CITI's implementation of pNFS/PVFS2
> 
> Alternatively you could point me to a mailing lists for users of
> pNFS/PVFS2 by the CITI group. I cannot seem to find a forum/group who
> discuss issues of pNFS/PVFS2 [if it is not this one]
> 
> My problem is as follows:
> 
> I want to use more than a single Metadata server [MDS] in CITI's
> pNFS/PVFS2. I use the instructions described here:
> 
> http://www.citi.umich.edu/projects/asci/pnfs/docs/pnfspvfs2.html
> 
> I understand these are not of the current build, but I am using an older
> build of pNFS/PVFS2.
> 
> Now if there are two or more MDS nodes, then how will clients mount the
> MDS nodes on a single mount point? I am familiar with the mount --bind
> argument
> [http://www.redhatmagazine.com/2007/03/19/how-do-i-mount-an-nfsv4-filesystem-in-two-locations-on-a-single-client/].
> Is this what we must do?
> 
> This situation arises on two occasions
> 1. When the MDS mounts a PVFS2 filesystem. Multiple MDS then mount the
> MDS PVFS2 filesystems at one point.
> 
> To quote from the instructions :
> 
> // Load kernel interface
> // Run on MDS
> insmod /usr/local/bin/pvfs2-server/pvfs2.ko
> /usr/local/bin/pvfs2-server/sbin/pvfs2-client -p
> /usr/lo:cal/bin/pvfs2-server/sbin/pvfs2-client-core
> mount -t pvfs2 tcp://"mds_server_hostname":3334/pvfs2-fs /mnt/pvfs2
> 
> 2. When the clients mount an NFS4 filesystem [essentially a PVFS2
> filesystem exported by the MDS]
> 
> To quote:
> 
> Step 7: Mount PVFS2 file system using pNFS
> 
>     * Copy /etc/pvfs2tab file to every client
>     * Example:
> 
>       // On client
>       insmod /usr/local/bin/pvfs2-layout/pvfs2-pnfs.ko
>       /usr/local/bin/pvfs2-layout/sbin/pvfs2-client -p
> /usr/local/bin/pvfs2-layout/sbin/pvfs2-client-core
>       mount -t nfs4 "mds_server_name":/ /mnt/nfs4/
> 
> 
> In both cases, multiple MDS cause the mounts to overlap. Although I have
> not tried this out, I suspect this is would result in an incorrect
> configuration.
> 
> Have you come across this issue when you worked with pNFS/PVFS2 before?
> 
> Thanks for your time.
> 
> Nirmal Thacker
> 
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