Mac OS X Time Machine backup disk

Time Machine is the backup application available with Mac OS X.

IBM® Storage Protect can be used at the same time as Mac OS X Time Machine application. However, due to the unique nature of how the Mac OS X Time Machine application backs up data, consider the following items before using the backup-archive client to back up the Mac OS X Time Machine data:

• The Mac OS X Time Machine backup disk makes extensive use of both file and directory hard links to minimize disk usage. For example, if the disk backed up with the Mac OS X Time Machine application is 5 GB, the first backup copies 5 GBs of data to the Mac OS X Time Machine backup disk.

  Subsequent backups only copy the files that have changed since the previous backup. All files and directories that have not changed are hard-linked with the version that was copied during the previous backup.

  The Finder shows each backup as 5 GB, for a total size of 10 GB. However, because of the use of hard links, the total disk usage is only slightly larger than 5 GB.

  All hard-linked objects that are not already on the IBM Storage Protect server are backed up.

  For example, 10 GB of data would be sent to the IBM Storage Protect server.

• When files that are restored are hard-linked, the client recreates the original hard link. Recreating the original hard link can only be done if all files that are hard-linked are restored at the same time. Restoring all the hard-linked files at the same time is not a practical method for a large backup disk that uses the Mac OS X Time Machine application.
• When the Mac OS X Time Machine application copies files to the backup disk, ACLs are added to the files to protect them from deletion. the backup-archive can back up and restore files with ACLs. However, any files that are restored must have these restrictive ACLs in place.

Tip: For best results, exclude the Time Machine application backup data. All Time Machine application data is in a directory named Backups.backupdb.