Where do mount options get stored in AIX?

AIX files system mount options (e.g. cio for db filesystems) can be seen in /etc/filesystems, but you could be forgiven for assuming that this is the only place. It’s true if you change the mount options in this file using vi and then remount the filesystem you will get the mount options you require. However you might not realise that they are actually stored in the VGDA of the fileystem as well. This causes the options to get overwritten as soon as you do an “importvg -L” or run a filesystem change through cspoc.

So if we have an example lv called fs01 mounted on /myfs,

if you read the header using od -c /dev/fs01|pg you will see the current options, in the below example they are just options=”rw”

0000520 v f s = j f s 2 : l o g  
 0000540 = / d e v / l o g l v 0 0 : m o  
 0000560 u n t = t r u e : **o p t i o n s**  
 0000600 = **r w** : a c c o u n t = f a l s  
 0000620 e  
 0000640

and read the the /etc/filesystems using

grep -p /myfs

/myfs:  
 dev = /dev/fs01  
 vfs = jfs2  
 log = /dev/loglv00  
 mount = true  
 check = false  
 options = rw,cio  
 account = false

You can see there is a difference between what /etc/filesystems sees and what is known on the lvm volume header.

So if a cluster operation (or sysadmin manually adding a new filesystem) ran an importvg -L {vgname} {hdisk} the change in /etc/filesystems would be overwritten and the next time the filesystem mounts you would loose your options.

So change your mount options using either chfs -a options=cio /myfs, or using cspoc on a powerha system, and you should see the following from the lv header od -c /dev/fs01|pg:

0000520 v f s = j f s 2 : l o g  
0000540 = / d e v / l o g l v 0 0 : m o  
0000560 u n t = t r u e : o p t i o n s  
0000600 = c i o , r w : a c c o u n t =  
0000620 f a l s e  
0000640

as well as the entry in /etc/filesystems