6.0 HP X9000 File Serving Software File System User Guide (TA768-96043, October 2011)

Tuning allocation policy settings
To optimize system performance, you can globally change the following allocation policy settings
for a file system:
• File allocation policy (see “File allocation policies” (page 155) for a list of available policies).
• Starting segment number for applying changes.
• Preallocation: Number of KB to preallocate for files. The default is a preallocated file size of
256 KB.
• Readahead: Number of KB in a file to pre-fetch. The default is 128 KB.
• NFS readahead: Number of KB in a file to pre-fetch on NFS systems. The default is 128 KB.
NOTE: Before tuning allocation policy settings, contact HP Support for guidance on selecting the
best values for your installation.
Use the following command to restore the default file allocation policy:
ibrix_fs_tune -f FSNAME {-h HOSTLIST|-g GROUPLIST} -p -U
Listing allocation policies
Use the following command to list the preferred segments (the -S option) or the allocation policy
(the -P option) for the specified hosts, hostgroups, or file system.
ibrix_fs_tune -l [-S] [-P] [-h HOSTLIST | —g GROUPLIST] [-f FSNAME]
HOSTNAME FSNAME POLICY STARTSEG DIRPOLICY DIRSEG
SEGBITS READAHEAD PREALLOC HWM SWM
mak01.hp.com ifs1 RANDOM 0 NONE 0
DEFAULT DEFAULT DEFAULT DEFAULT DEFAULT
158 Using file allocation