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Configuring NFS and Samba servers to export Lustre file systems5–6

5.1.6 Optimizing NFS server performance

To optimize NFS performance, consider the following recommendations for the configuration on the HP SFS

client node that has been configured as an NFS server:

• As part of the installation of the HP SFS client software on client nodes, the kernel on the client node

is patched to provide support for Lustre file systems. In addition, patches are supplied to improve NFS

client system read performance. Included in these patches is a variable that allows you to tune the

NFS performance on the NFS server, as follows:

/proc/sys/lustre/nfs_readahead

This variable sets the number of kilobytes that will be read ahead when the NFS server is performing

sequential I/O from a Lustre file system. For optimal NFS client system performance, HP recommends

that you set this variable to 64.

This value lets Lustre know that a minimum of 64KB is to be read ahead. This amount is sufficient to

assist the NFS 32KB requests that the client node will request.

The recommended setting is based on having the stripe size configured as recommended in

Section 5.1.4.

When you are tuning the nfs_readahead value, start with a value of 64KB and increment it as

needed to achieve maximum read performance.

HP recommends that you increment the value in steps of 32KB.

• HP recommends that the /proc/sys/portals/debug value is set to 0 (zero). (Note that the value

of this variable may already be set to 0 (zero); if this is the case, you do not need to make any

change to it.)

• Because NFS Version 3 client systems exert pressure on the NFS server’s virtual memory subsystem,

HP recommends that the NFS server utilizes multiple disks to provide storage area for paging.

5.2 Configuring Samba servers

HP SFS allows Windows® and CIFS (Common Internet File System) client systems to access Lustre file systems

via Samba.

To use Samba to access Lustre file systems, you must configure one or more HP SFS client nodes as Samba

servers. There are many configuration options for a Samba server; please consult the Samba documentation

for the configuration information. You can find more information about Samba at http://www.samba.org

When configuring HP SFS client nodes as Samba servers to export Lustre file systems, you must take the

following constraints into consideration:

• Only one Samba server may be configured to export any given Lustre file system or subdirectory of a

Lustre file system.

This limitation is due to the cache consistency and locking models that are implemented by Samba.

• A Lustre file system may be exported over NFS or over Samba, but may not be exported over both

NFS and Samba at the same time.

• Multiple HP SFS client nodes configured as Samba servers may export different Lustre file systems via

Samba (but they may not export the same Lustre file system or subdirectories of the same Lustre file

system, as stated earlier).

• When stopping a Lustre file system that has been exported over Samba, you must first stop the Samba

server before you stop the Lustre file system.

• In the smb.conf configuration file on the Samba server, you must specify use sendfile = no as

an active option.

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