Reducing FS with OJFS

[John Lipsitz]

Hi,

ive heard OnlineJFS 3.3 will allow you to reduce a mounted filesystem by moving any data (used inodes) out of the way - which previous versions of OJFS would not do. Is this the case ?

[James R. Ferguson · Accepted solution]

Hi:

Yes, from document #JFS0007:

The new version 4 disk layout supported by OnlineJFS 3.3 allows successful online file system reduction.

In previous JFS releases, file system reduction failed when there was file system data in the area to be reduced.

With version 4 disk layout, JFS tries to move data from the area to be reduced to another part of the file system.

If JFS successfully relocates the data, the reduction takes place. If JFS cannot move the data, the reduction fails.

...JRF...

[Carol Garrett]

In a version 3 or above disk layout (JFS) if there are files in use on the sectory you wish to reduce then OJFS will attempt to relocate them to the filesystem space which is not being reduced.

Ive used this, it seems to work most of the time. Sometimes if your trying to reduce your filesystem too far to the used space total (eg. 1Gb FS, only 200Mb used, sometimes you cant reduce right down to 200Mb - may need to go to 250Mb or so) or if you have lots and lots of files on the filesystem you dont seem to be able to reduce too far also, even running a drfrag (fsadm -e). So its not guaranteed to reduce, but its a lot better than the old type 2 disk layout which couldnt be reduced at all if there was a file on the part of the filesystem you wanted to reduce.