Data migration

Before you can use your existing data in SAN File System, you must first migrate it to the SAN File System global namespace.

Tip: If you are migrating a large amount of data, thoroughly plan the migration in advance, to reduce the risk of error and to minimize downtime to your organization.

You must perform data migration from the client machine. Data from a Windows-based application must be migrated from a Windows-based client. Likewise, data from an AIX® application must be migrated from an AIX client.

You can use standard copy commands or utilities that are provided by the client operating system to migrate your data (for example, cp, cpio, or tar commands on AIX; and the xcopy command or Explorer on Windows®). You can also use backup applications to restore data from the latest backup into the SAN File System as the destination. These methods work best when migrating large numbers of small files.

For migrating large files, SAN File System provides a data migration utility, called migratedata, to help migrate your data quickly and efficiently, while preserving the file attributes (such as owner, group, and creation time) of your files. This utility is optimized for bulk data movement of a small number of large files. It includes these features:
The migratedata utility migrates only the following objects: All other objects in the existing file system are ignored.

The migratedata utility attempts to preserve all hard links to regular files. For UNIX-based clients, if SAN File System is set up in such a way that hard links traverse across a fileset, the hard links are replaced with a symbolic link.

You cannot use file-system-based compression (as with NTFS) with SAN File System; however, you can file-based compression (for example, files produced by utilities such as compress on AIX systems and ZIP utilities on systems running the Microsoft® Windows operating system). During the migration process, all compressed files are expanded.

Migrating data using the data migration utility is a disruptive process. This means that, to guarantee data integrity, you must stop all applications and users from modifying the data being migrated (including database and application servers) until the migration is complete. Only the data being migrated must remain unchanged. To minimize the impact of a migration, you can migrate your data in chunks rather than all at one time.

If you are migrating a database environment, the procedures vary depending on whether your environment is file-system based or contains raw configuration devices. For a file-system-based environment, use the migratedata utility to migrate your files, and then reconfigure the database application to reflect the data movement. For raw configuration devices, an unload command to move data out of the raw devices to a temporary holding location, and then perform a load operation to place the data in its location in the global namespace. After the data is loaded into the global namespace, it is file based.

Tip: If you are migrating a Microsoft Exchange database from NTFS to SAN File System, use tools that come with Exchange rather than the migratedata utility to ensure that the user configuration data and parameters are also migrated.
Important:
  1. The data migration utility does not prevent an application or user from modifying (for example, editing, moving, or deleting) the data being migrated. Make sure that no one modifies this data.
  2. The migratedata utility writes different parts of a single file in parallel; therefore, there is no guarantee that the file data will be densely allocated. Operating system utilities that copy data sequentially (such as cp and xcopy) do result in densely allocated file data.
  3. On Windows-based clients, migrating from the root of any volume to SAN File System using the migratedata utility can set the destination directory to system and hidden. This is as designed because any root volume on NTFS is set to system and hidden.
  4. During migration, if there are no other applications running on an AIX-based client, shut down the operating system daemon syncd before you start the migration process.

Parent topic: Concepts

Related tasks
Migrating data

Related reference
Data-migration considerations

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