1*4882a593Smuzhiyun 2*4882a593Smuzhiyun================================== 3*4882a593SmuzhiyunpNFS SCSI layout server user guide 4*4882a593Smuzhiyun================================== 5*4882a593Smuzhiyun 6*4882a593SmuzhiyunThis document describes support for pNFS SCSI layouts in the Linux NFS server. 7*4882a593SmuzhiyunWith pNFS SCSI layouts, the NFS server acts as Metadata Server (MDS) for pNFS, 8*4882a593Smuzhiyunwhich in addition to handling all the metadata access to the NFS export, 9*4882a593Smuzhiyunalso hands out layouts to the clients so that they can directly access the 10*4882a593Smuzhiyununderlying SCSI LUNs that are shared with the client. 11*4882a593Smuzhiyun 12*4882a593SmuzhiyunTo use pNFS SCSI layouts with the Linux NFS server, the exported file 13*4882a593Smuzhiyunsystem needs to support the pNFS SCSI layouts (currently just XFS), and the 14*4882a593Smuzhiyunfile system must sit on a SCSI LUN that is accessible to the clients in 15*4882a593Smuzhiyunaddition to the MDS. As of now the file system needs to sit directly on the 16*4882a593Smuzhiyunexported LUN, striping or concatenation of LUNs on the MDS and clients 17*4882a593Smuzhiyunis not supported yet. 18*4882a593Smuzhiyun 19*4882a593SmuzhiyunOn a server built with CONFIG_NFSD_SCSI, the pNFS SCSI volume support is 20*4882a593Smuzhiyunautomatically enabled if the file system is exported using the "pnfs" 21*4882a593Smuzhiyunoption and the underlying SCSI device support persistent reservations. 22*4882a593SmuzhiyunOn the client make sure the kernel has the CONFIG_PNFS_BLOCK option 23*4882a593Smuzhiyunenabled, and the file system is mounted using the NFSv4.1 protocol 24*4882a593Smuzhiyunversion (mount -o vers=4.1). 25