206 IBM Tivoli Storage Manager Versions 5.4 and 5.5 Technical Guide
16.1 Hierarchical Storage Management
IBM Tivoli Storage Manager for HSM for Windows (referred to subsequently as the “HSM
client”) provides Hierarchical Storage Management (HSM) services for Windows NTFS file
systems under Windows 2003. Using the HSM client, individual files from directories or
complete NTFS file systems can be migrated to remote storage in an IBM Tivoli Storage
Manager server (any platform). The migration can be controlled by a policy that can include
parameters like file size, age, or last access. If you use a policy, only files that match the
policy rules are migrated.
The HSM client always supports one version below, the equal version or one version higher
than the HSM client version with regards to the Tivoli Storage Manager server level. This is
called n+/-1 support. As an example, an HSM client V5.4 is supported with a Tivoli Storage
Manager server V5.3, V5.4, or V5.5.
The HSM client acts as a Tivoli Storage Manager client. It uses the Tivoli Storage Manager
client’s archiving API. Migrated files from the HSM client are stored in native
archive storage
on the Tivoli Storage Manager server (defined with TYPE=ARCHIVE on the DEFINE
COPYGROUP command), not in HSM pools (MIGDESTINATION on the DEFINE
MGMTCLASS command), which are used only by the Tivoli Storage Manager for Space
Management client (HSM for UNIX). We recommend setting the retention for the archive copy
group that is used to NOLIMIT.
A migrated file leaves a small piece of the file (stub file) on the NTFS file system. Stub files
contain the necessary metadata to recall the migrated files. The metadata information
includes the Tivoli Storage Manager server (where the files are migrated to) and the file
server (where the files are migrated from). A reparse point is attached to the stub file and
builds the interface for HSM for Windows to the NTFS file system. A reparse point has a
Microsoft registered reparse ID, which is world-wide unique. At any time that an application
tries to access the content of a stub file (with an HSM client reparse point), the file system
filter of the HSM client is informed about this and HSM can recall the file.
Attention: The host name, IP port, and server name of the Tivoli Storage Manager, as well
as the host name of the file server, are included in the stub file. If you change any of these
Tivoli Storage Manager server settings, or the host name of the file server, files previously
migrated will not be able to be recalled.
Chapter 16. HSM for Windows V5.4 207
Figure 16-1 on page 207 shows an HSM for Windows environment including the Tivoli
Storage Manager server and client.
Figure 16-1 HSM environment
The migration of files is transparent to Windows users and applications. That is, Windows
users can see and access migrated files like any other file that is present on the file system.
The difference is that when a migrated file is opened, it will be transparently retrieved and
copied back to the local Windows system. You can identify migrated files by the changed file
icon (Figure 16-2) and the offline attribute that is set in Windows Explorer, as shown in
Figure 16-3.
Figure 16-2 Different icons before and after migration
TSM Server
Storage Pool
Storage Pool
File System
Windows File Server
File W
Stub W
File W
208 IBM Tivoli Storage Manager Versions 5.4 and 5.5 Technical Guide
Figure 16-3 Migrated files with the HSM client
The changed file icon is also called an overlay icon, which the operating system puts over the
existing icon to indicate the state of the file. Windows XP or Windows Server 2003 adds a
clock to the icon. As shown in Figure 16-2, Windows Vista uses a cross (x) instead of a clock.
Figure 16-4 shows the file properties. The difference between the Size and Size on disk fields
allows you to identify a migrated file. The Size field still shows the original file size, while the
Size on disk field shows the actual file size of the stub file, which is one cluster of the disk.
The cluster size is mostly 4 KB, but it can be larger, depending on the disk configuration.
Figure 16-4 Migrated file properties

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