| pNFS block layout server user guide |
| |
| The Linux NFS server now supports the pNFS block layout extension. In this |
| case the NFS server acts as Metadata Server (MDS) for pNFS, which in addition |
| to handling all the metadata access to the NFS export also hands out layouts |
| to the clients to directly access the underlying block devices that are |
| shared with the client. |
| |
| To use pNFS block layouts with with the Linux NFS server the exported file |
| system needs to support the pNFS block layouts (currently just XFS), and the |
| file system must sit on shared storage (typically iSCSI) that is accessible |
| to the clients in addition to the MDS. As of now the file system needs to |
| sit directly on the exported volume, striping or concatenation of |
| volumes on the MDS and clients is not supported yet. |
| |
| On the server, pNFS block volume support is automatically if the file system |
| support it. On the client make sure the kernel has the CONFIG_PNFS_BLOCK |
| option enabled, the blkmapd daemon from nfs-utils is running, and the |
| file system is mounted using the NFSv4.1 protocol version (mount -o vers=4.1). |
| |
| If the nfsd server needs to fence a non-responding client it calls |
| /sbin/nfsd-recall-failed with the first argument set to the IP address of |
| the client, and the second argument set to the device node without the /dev |
| prefix for the file system to be fenced. Below is an example file that shows |
| how to translate the device into a serial number from SCSI EVPD 0x80: |
| |
| cat > /sbin/nfsd-recall-failed << EOF |
| #!/bin/sh |
| |
| CLIENT="$1" |
| DEV="/dev/$2" |
| EVPD=`sg_inq --page=0x80 ${DEV} | \ |
| grep "Unit serial number:" | \ |
| awk -F ': ' '{print $2}'` |
| |
| echo "fencing client ${CLIENT} serial ${EVPD}" >> /var/log/pnfsd-fence.log |
| EOF |
