free space needed by OnlineJFS

[Alex Georgiev]

Does any know how much free space has to be available for fsadm to extend a file system online?

I know it's a small number, but how small?

I'm creating "buffer" files...

[Steven E. Protter]

Shalom Alex,

Any free PE's should permit you to extend the filesystem online. The minimum depends on the number of PE's per block. 4 is the default, but you can change that when you create the volume group.

SEP

[Raj D.]

Alex,

check your PE size and Free PE on that volume group. Multiply PE_Size*Free_PE = Result , that can you can extend. Further you need to check with vgdisplay command, and to calcute.

check with :

# vgdisplay -v /dev/vgxx | grep -e Free -e dsk


cheers,
Raj.

[Alex Georgiev]

Sorry guys, I think I stated the question wrong.

What I need to find out is this:

If a file system becomes 100% full, then it can not be extended with Online JFS. It has to be dismounted and extended with the extendfs command instead.

So Online JFS needs a little bit of free space in order to be able to extends a file system. Question is how much?

[Sandman!]

By default the FS is not really full and the bdf report has a factor of safety built into it so all you really need to do is identify free extents in your VG that contains the lvol, lvextend the exisitng lvol onto it and then fsadm the mount point w/o having to unmount the filesystem.

hope it helps!

[A. Clay Stephenson · Accepted solution]

Only a very small amount. There must be enough room to create a lost+found directory (which should already be there) and the .fsadm lock file under this directory. If the lock file can't be created; fsadm fails. My best guess is there must be at least 1 block left in an allocation unit (assuming that the lost+found directory) is already there. Of course, admins that are doing their job will detect this long before the filesystem actually fills up and take appropriate action.

[Alex Georgiev]

Alas, not all admins can prevent SQL report writers from filling up volumes in the blink of an eye in the middle of the night. :-)

[Bill Hassell]

AS mentioned, there should be enough free space for fsadm even when creating additional files will cause a filesystem full message.

As far as report writers filling important filesystems, I usually have good luck by asking the DBA manager for 500Gb of extra disk space just for the reports. I also move the DBA's HOME directories to the samed volume so when they don't monitor their space, they can't login. Usually the giant disk space request will create smaller (and less) reports.