HP XC System 3.x Software - Manual (Page 21)

nodes must be launched from nodes with the login role. Nodes with the compute role
are referred to as compute nodes in this manual.
1.1.5 Storage and I/O
The HP XC system supports both shared (global) and private (local) disks and file systems. Shared file
systems can be mounted on all the other nodes by means of Lustre or NFS. This gives users a single view
of all the shared data on disks attached to the HP XC system.
SAN Storage
The HP XC system uses the HP StorageWorks Scalable File Share (HP StorageWorks SFS), which is based
on Lustre technology and uses the Lustre File System from Cluster File Systems, Inc. This is a turnkey
Lustre system from HP. It supplies access to Lustre file systems through Lustre client/server protocols
over various system interconnects. The HP XC system is a client to the HP StorageWorks SFS server.
Local Storage
Local storage for each node holds the operating system, a copy of the HP XC System Software, and
temporary space that can be used by jobs running on the node.
HP XC file systems are described in detail in “File System” .
1.1.6 File System
Each node of the HP XC system has its own local copy of all the HP XC System Software files including
the Linux distribution; it also has its own local user files. Every node can also import files from NFS or
Lustre file servers. HP XC System Software uses NFS 3, including both client and server functionality. HP
XC System Software also enables Lustre client services for high-performance and high-availability file I/O.
These Lustre client services require the separate installation of Lustre software, provided with the HP
Storage Works Scalable File Share (SFS).
NFS files can be shared exclusively among the nodes of the HP XC System or can be shared between the
HP XC and external systems. External NFS files can be shared with any node having a direct external
network connection. It is also possible to set up NFS to import external files to HP XC nodes without
external network connections, by routing through a node with an external network connection. Your
system administrator can choose to use either the HP XC administrative network or the HP XC system
interconnect for NFS operations. The HP XC system interconnect can potentially offer higher performance,
but only at the potential decrease in the performance of application communications.
For high-performance or high-availability file I/O, the Lustre file system is available on HP XC. The Lustre
file system uses POSIX-compliant syntax and semantics. The HP XC System Software includes kernel
modifications required for Lustre client services which enables the operation of the separately installable
Lustre client software. The Lustre file server product used on HP XC is the HP StorageWorks Scalable File
Share (SFS), which fully supports the HP XC System Software.
The SFS also includes HP XC Lustre client software. The SFS can be integrated with the HP XC so that
Lustre I/O is performed over the same high-speed system
interconnect fabric used by the HP XC. So, for
example, if the HP XC system interconnect is based on a Quadrics® QsNet II® switch, then the SFS will
serve files over ports on that switch. The file operations are able to proceed at the full bandwidth of the
HP XC system interconnect because these operations are implemented directly over the low-level
communications libraries. Further optimizations of file I/O can be achieved at the application level using
special file system commands – implemented as ioctls – which allow a program to interrogate the
attributes of the file system, modify the stripe size and other attributes of new (zero-length) files, and so
on. Some of these optimizations are implicit in the HP-MPI I/O library, which implements the MPI-2 file
I/O standard.
File System Layout
In an HP XC system, the basic file system layout is the same as that of the Red Hat Advanced Server 3.0
Linux file system.
The HP XC file system is structured to separate cluster-specific files, base operating system files, and
user-installed software files. This allows for flexibility and ease of potential upgrades of the system software
SAN Storage 21