Wednesday, July 20, 2011

What is Minfree space?

File system minfree space:

1. The portion of a file system that is reserved and held back from users.

2. It is accessible by root.

3. On large file systems, the minfree is automatically determined so that disk space is not wasted.

4. A thumb rule is to use default 10% minfree value for file systems upto 1GB and then adjust the minfree value so that your minfree area is no larger than 100MB>

5. Note: As for performance, applications do not complain about the lower minfree value.

To view the minfree value of a slice:

# fstyp -v /dev/dsk/c0t12d0s0 | grep -i min

minfree 10% maxbpg 2048 optim time

To change the minfree value:

# tunefs -m 1 /dev/dsk/c0t12d0s0

minimum percentage of free space changes from 10% to 1%

In the same way, the minfree space can be increased.

1 comment:

  1. Sollin Selvan - 1. We need space to execute commands on the slice/mount point.
    2. Moreover most of Unix commands are external commands.
    Hence we reserve some space to every slice and termed as minfree space.