Appendix B. Case study: IBM Global Storage Architecture 323
because the node running Tivoli Storage Manager reads the data from the
SAN-attached disks and writes it back to tape on the SAN.
Two copy pools of the data are kept on site to protect against tape failures. An
additional copy is sent off site to safe storage.
Time synchronization
Time synchronization is extremely important within any enterprise file system.
The time stamps on files and directories are updated by file servers in certain
instances, and directly by clients in others. This can lead to problems if the clocks
are not synchronized across the system. Systems that use Kerberos must also
have clocks synchronized within a certain window.
Technically speaking, it is not impor