This document describes how to move a journaled file system (JFS) from one volume group to another. Information in this document applies to AIX Versions 4.x.
For more in-depth coverage of this subject, the following IBM publications are recommended:
IBM documentation can also be found online at the following URL:
http://www.rs6000.ibm.com/resource/aix_resource/Pubs/index
.html
ATTENTION: Make sure a full backup exists of any data you intend to migrate before using these procedures.
In AIX, storage allocation is performed at the volume group level. Storage cannot span volume groups. If space within a volume group becomes constrained, then space that is available in other volume groups cannot be used to resolve storage issues.
The solution to this problem is to add more physical volumes to the relevant volume group. This may not be an option in all environments. If other volume groups contain the required free space, the alternative is to move the required logical volumes to the desired volume group and expand them as needed.
The source logical volume can be moved to another volume group with the cplv command. The following steps achieve this.
ATTENTION: The logical volume should be inactive during these steps to prevent incomplete or inconsistent data. If the logical volume contains a mounted file system, then that file system should be unmounted first. If this logical volume is being used as a RAW storage device, then the application using this logical volume should close the device or be shut down.
For example, where myvg is the new volume group and mylv is the name of the user's logical volume, enter:
cplv -v myvg mylv
This will return the name of the new logical volume, such as lv00.
If this logical volume was being used for RAW storage, skip to to step 6. If this is a JFS file system, proceed to step 2. Please note that RAW storage devices should NOT use the first 512 bytes of the RAW device. This is reserved for the LVCB or logical volume control block. cplv will not copy the first 512 bytes of the RAW logical volume, but it will update fields in the new logical volume's LVCB.
To make a new JFS log, enter the following command, where myvg is the name of the new volume group, enter:
mklv -t jfslog myvg 1
This will return a new JFS log logical volume such as loglv00. This will need to be formatted with the logform command to function as a JFS log. For example:
logform /dev/loglv00
Answer yes to destroy.
For example, where myfilesystem is the name of the user's filesystem, enter:
chfs -a dev=/dev/lv00 -a log=/dev/loglv00 /myfilesystem
fsck -p /dev/lv00
For example, where myfilesystem is the name of the user's file system, enter:
mount /myfilesystem
At this point, the migration is complete, and any applications or users can now access the data in this filesystem. To change the logical volume name, proceed to the following step.
NOTE: If you receive errors from the preceding step, do not continue. Contact you AIX support center.For example, where mylv is the name of the user's logical volume, enter:
rmlv mylv
For example, where mylv is the name of the user's logical volume, enter:
chlv -n mylv lv00
The following logical volumes and file systems are specific to the rootvg volume group and cannot be moved to other volume groups:
Logical Volume File System or Description
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hd2 /usr
hd3 /tmp
hd4 /
hd5 <boot logical volume>
hd6 <primary paging space>
hd8 <primary JFS log>
hd9var /var
[ Doc Ref: 90605212014776 Publish Date: Mar. 05, 2001 4FAX Ref: 9088 ]