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Mount Option

Mount Description

acdirtimeo

Seconds to cache directory attributes. The shorter this value, the more frequently

communication to HPSS is required. Synchronization between separate vfs nodes

or mount points may benefit for a shorter cache period with the expense of longer
latencies.

flushd

The flush deamons look for data pages that need to be written to HPSS, either time

to write or data pages being requested for other files. Each daemon consumes

resources so care should be taken when changing this option. Another possibility is
to change iomax to allow more pages to be available.

rtimeo / wtimeo

Performance gains can be realized when minimizing the number of transfers. This
timeout allows multiple requests to be combined within the time limit.

rpages / wpages

Each specifies the maximum number of kernel buffer pages that can be dedicated to

individual file transfers. Care must be taken to configure this correctly to the
expected number of concurrent transfers and the iomax mount option.

iomax

Maximum number of kernel buffer pages (4096 bytes + overhead) that can be

allocated for data buffers when transferring file data. Each mount point has its own
set of data buffers. Since these pages consume

RAM

resources, this must be

compatible with application loads and transfer goals for the system. For instance,
the more pages allocated to the mount point, the less RAM

available for

applications. This should also be consistent with rpages and wpages.

fcsize

File Cache Size. Cache this much of the file on first access. This consumes

resources so care must be taken not to make this too large. Configuring this to

typical file access patterns will speed access when large enough to cache future
requests.

san / nosan

Configures the mount point to transfer data from buffers directly to SAN

devices.

shm

Shared Memory (need to look into this)

dio

Configures the mount point to transfer data to/from directly from application space.

This bypasses Linux VFS file buffering, see ???? for a discussion on advantages
that the Linux VFS buffering provides.

trace

Level of messages logged from the HPSS kernel extension to /var/log/messages.
Ranges from 0 to 5 with 0 being the least and 5 being lots.

sharefd / nosharefd

rattr

Typically short directory listings do not have to access HPSS for file attributes.

Specifying this option will force all directory listings to retrieve file attributes from

HPSS. If the application is always doing long directory listings this has no effect. If

the application always requests short directory listings, this will delay those requests
needlessly.

Configure the network interfaces to use.

cos

Specify the default Class Of Service to use. This can be overridden by an ioctl()

system call once the file is created but BEFORE any data is written. Standard Linux
commands / library functions will not use the ioctl(), they will use the COS

setting for

files stored in a fileset.

ro / rw

File system will be ro=read only or rw=read write.

maxsegsz

Use the maximum segment size for the storage class. If not used, the minimum

segment size is used. An application can use ioctl() to set this per file once the file is
created but BEFORE any data is written.

HPSS Management Guide

November 2009

Release 7.3 (Revision 1.0)

353