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- 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 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
- .. code-block:: sh
- #!/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
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