fsexpand - expand existing file systems

fsexpand enables file systems to be expanded by PAM pages or cylinder groups. The file systems may not be mounted.

Syntax

fsexpand[ -i][ -p pam_pages| -c cylinder_groups] device

-i

Outputs file system information. Output takes place to stdout. In particular information is output on how ideal an expansion is, e.g. to prevent unused PAM pages in the expanded file system. In conjunction with the -p or -c option, information is output before the expansion (source file system) and after the expansion (target system).

-p pam_pages

Expansion of a file system by PAM pages.

The file system is expanded by the specified number of PAM pages.

-c cylinder_groups

Expansion of a file system by cylinder groups.

The file system is expanded by the specified number of cylinder groups. The size of a cylinder group in the source file system can be ascertained before expansion using fsexpand -i. Up to a file size of a little more than 2 GB, the size is 2048 PAM pages. From 2 GB on, the size increases. With a file size of 4 GB, for example, it is then 4096 PAM pages.

device

Device name /dev/rdsk/... (character-oriented device only, i.e. not /dev/dsk) or BS2000 file name.

device must be writeable when an expansion is to take place. If the file system is located on the HOME pubset, the BS2000 file name (with or without catid) must match the notation in the /etc/partitions file.

Hints

The fsexpand command is not supported for bs2fs file systems.

A file system is expanded in two steps:

1. Physical expansion

2. Combining (administration) units of the file system (known as cylinder groups) to form
   larger units (compactification)

   Compactification is performed only if the expanded file system is greater than 2 GB and
   at least double the size of the original file system.

Compactification requires a considerable amnount of the runtime for fsexpand. If, for example, a file system which is 1 GB in size is expanded by a value which is only slightly above 1 GB (i.e. with compactification), the runtime is extended by a factor of 3 - 4 compared to expansion by a value which is slightly less than 1 GB (i.e. without compactification). However, compactification has the advantage that considerable gains in performance can be achieved when the file system is used because at runtime the requirement for memory and CPU time is lower thanks to the administration units being combined.

Example

# fsexpand -i /dev/rdsk/2

device /dev/rdsk/2 in Containerfile: $SYSROOT.FS.OPT

size of BS2000 Containerfile (PP):   796674
size used for POSIX filesystem (PP):         796672
unused in Containerfile (PP):                2
Cylindergroups in filesystem:                389
Cylinders in cylindergroup:          16
size of a cylindergroup (PP):                2048
inodes per cylindergroup:            2048
inodes total:                                796672
datablocks(4K) in filesystem:                371878
        free blocks(4K)         directories             free inodes 
        187993                  1550                    785959
optimal values for expansion of container: 2046 PP + N * 2048 PP