A typical AIX system administrator problem is the importance of these systems, and being not able to stop them at anytime & for any reason. A downtime on these AIX boxes are very expensive and the admin has to avoid at all cost. In the other hand, its often the case where the admin has to move the data from one disk to another without losing data. Furthermore, the admin has to avoid downtime while handling the migration. Few typical reasons why the admin need to migrate data between different disks or even storages are:

• The requirment to move to a larger disk
• The requirement to move to a different Raid Configuration disk
• The requirement to move from local disk to the SAN or any other external disk
• The requirement to move to a new VG configuration

The above reasons are just a few reasons why you would need to migrate data between different disks on AIX. As these AIX Servers has to always stay online, below is the method to migrate the data between disks with the least amount of downtime possible, even no downtime in most situations :).

The first thing to ensure is the new disk is hot plug ready, so it does not required a downtime to attach it to the system. Most SAN & disks in the market today are HOT-SWAP ready.  So ensure you get one of these.

OK, the basic idea of this exercise is to avoid stopping the services while moving the data between the old disk /LUN (hdisk1) to the new disk/LUN (hdisk2). This is done by avoiding to stop the service to use LVM. Below is the instruction:

1-  Attach the new disk (hdisk2) and ensure its available to the system
# cfgmgr
# lsdev -Cc disk

2- Add the disk to the volume group where the FS (datasvg)
# /usr/sbin/extendvg datasvg hdisk2

3-  Move logical volumes of disk origin (hdisk1) to the new disk (hdisk2)
# /usr/sbin/migratepv hdisk1 hdisk2

4- Remove the original disk (hdisk1) of
# /usr/sbin/reducevg datasvg hdisk2

5- Finally, we note that the original disc contains nothing new or that the disk contains the file systems
# lspv -l hdisk1
# lspv -l hdisk2

Ah I hope that help you avoid one of these ugly downtime where your boss has to give you a hard time before approving it. Please leave a comment with your success story & experience with the above instruction :).