AIX > Tips & Techniques > Systems Management

Moving Mounts

Move large file systems with ease

File systems allow you to group your data according to its usage. For example, you can separate database log files from the physical database files by placing them in different file systems. That way you can tailor each file system, and the storage it uses, to suit the workload.

Some tasks can be done for an entire file system, which would be difficult or sometimes impossible to do for individual directories and files contained in the file system. You can tune, back up, secure, move or remove an entire file system. A well-designed file-system layout can be a great help for managing disk usage and performance. You can list file names and statistics for a file system using the df command (see Resources).

Mount View

Every file system has a mount point. This is a directory, which serves as the entry point for the file system. The mount point is the root directory of the file system. You can see mount points in the output of the df command. This also shows the logical volume name for each file system in the “Filesystem” column (see Figure 1).

File system mount points, like host names, are often set up to reflect their role within the organization’s infrastructure. A file system's mount point can be chosen for many different reasons, for example:

• A company or department name (e.g. /acme/finance)
• File-system function (/usr/scripts, /backup, /db2home)
• Database instance and file type (/oracle/SID1/sapdata1, /oracle/SID1/origlogA)
• Branch or geographic location (/reports/london)

File system mount points can be instructive, but no matter how well you plan your file-system structure, file systems can outlive their original mount point names. After a while their names can become obsolete, if not misleading. There are plenty of reasons why that might happen: organizational restructures, system consolidations, moving to a new host or site or maybe just a change of naming conventions. If the file-system name needs to change, you somehow need to get the data to sit under a completely new directory structure.

A Big Move

If you have to move all of the data in a file system, you could create a brand new file system, then copy, move or restore the data. A simpler way is to change the file system mount point. After all, creating a new file system and moving the data is a lot of work. It requires new storage to be allocated, and if there’s been some tweaking for performance on the original disk, it’ll have to be carried through to the new disk. A new file system would need to be built with similar characteristics to the original one. Then there’s the time it takes to move the data. If it's a large amount of data or if there are thousands of files to move it could involve a lot of downtime. Once the data move is done and verified, you'd have to do a cleanup of the old file system and storage.

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