By Graham K. Rogers

System Preferences has seen a fair number of changes with the update to OS X 10.8, Mountain Lion. Some of these are less evident than others. The Time Machine preferences panel has received a number of changes, but these are mainly under the surface and there are differences in the way the feature now operates.

Time Machine enables backing up of the entire contents of an OS X system to a specified external disk. Apple expanded the function with Time Capsule and in the update to OS X: 10.7, Lion, Time Machine was altered to make day to day operations more efficient, including the ability to back up when a disk was not connected. It is therefore now possible to view the Time Machine "Infinity" display whenever the Dock icon is pressed, once a Disk has been specified and set up.

With Mountain Lion a new possibility appeared -- the ability to use more than one disk for backing up -- and I was alerted to this by Rob LeFebvre on Cult of Mac and also in a more technical article by Topher Kessler.

Setting Up (1)

In this original setup condition, the main panel has a revised text description of the feature. At the bottom is a check box for display of the icon in the menu bar: this additional icon provides other controls when active. These are related to the Preferences, but are not identical.

Changing Off to On (or using the Select button) brings down a panel in which a user may highlight a suitable disk for backups to use. Initially this also has an icon for Time Capsule -- Apple's hard disk and Wi-Fi combination. Any hard disk attached will also become visible.

When Select Disk is pressed, there are a number of options. Any usable disk connected is recognized. It may be selected by highlighting it and pressing the "Use for Backup" button. A second button enables a user to set up Time Capsule. Pressing that button links to the Airport setup utility. The panel revealed when selecting a disk for the feature will depend on the type of computer: a notebook, for example, will have a checkbox to allow use of the backup disk when using battery only.

While Time Capsule is ready to run, a hard disk purchased from a store may need to be partitioned. This may be done beforehand in Disk Utility (in Applications > Utilities) and choosing the Partition tab. Once the size of the partition (or partitions) is decided, press the Options button and choose Apple Partition Map or GUID. However, when experimenting with a new disk (see below) that had a partition in the FAT 32 format, Time Machine set this up for me without the need for my intervention.

The system recognizes any disk made available and the main part of the panel changes. The disk icon is moved to the left and details of the disk used are displayed: Name, Available (disk space), Oldest Backup, Latest Backup and Next backup. If backing up, a progress bar is displayed.

Setting Up (2)

The new ability to use more than one disk offers a number of possibilities, such as backup disks in separate locations; or an easy transition from a full disk to its replacement.

With a number of disks and partitions available, I selected one that was offered. A panel appeared asking me if I wanted to replace the current backup disk or Use Both. I selected the latter and the display in the main panel changed to indicate the new options. Unfortunately the partition was too small for the amount of data I have and, although the backup started, it was cancelled by OS X.

I later removed that disk from the list of options and the display returned to its normal one-disk setup.

[This was a warning that the 500 GB disk is too small and I priced a 1 TB disk the next afternoon.]

Backing Up

The first backup takes a long time. If there is more than one partition on the external disk, the transfer may be slowed if Spotlight indexes the others. Spotlight preferences can be used to drag the partition icon to the "Privacy" panel. Indexing will stop.

In Snow Leopard and before, whenever the disk was connected, the entire system was backed up every hour, every day and every week. This changed with Lion and the Options panel had an entry to Lock Documents. This has gone. Documents can be locked in some applications only (e.g. TextEdit) by clicking on the title at the top centre: a number of options are revealed.

Time Machine does not create a total clone. Any changes are recorded and Time Machine uses those for an incremental backup. The preferences do not have to be open for backups to occur.

When the disk is available, the information ("When disk is connected") changes to a progress bar during a backup. Sometimes there will be a striped bar showing, "Preparing backup." This may be for a long time if there has been a problem or a gap in backing up: patience is the key here.

To force a backup, we can use the Backup Now item in the Dock or the menu bar icon menu. If a backup fails, information appears in red, with the letter i in a red circle alongside. The "i" can be clicked to reveal more information about the problem. Trying again (or perhaps a restart if this is persistent) will usually clear the problem.

At the bottom of the main display the Options button reveals a panel with some extra features. We may prevent backing up of specific items (e.g folders, files) by use of a + icon below the main window, marked "Exclude these items from backups" (the - alongside will remove list items). The screen shot used (above) was when the extra backup disk was being set up: the partitions were added automatically.

Pressing + opens a Finder window (by default mine opened in Applications). There are two options here: Cancel and Exclude (default). At the bottom of that window is a checkbox marked, "Show invisible items".

Two checkboxes at the bottom of the "Exclude" panel are marked Back up while on battery power (not on desktop computers); and Notify after old backups are deleted. As the disk becomes filled, so the earliest backup will be removed to make room for the current ones. This may also be considered a warning that it is time to obtain a new disk.

Restoring

This feature works best when a disk is attached, but it will function up to a point without. In testing (7 September) I was able to return to 31 August with no Time Machine disk attached. Even this can be a lifesaver, for example with a version of a file, or an item that was accidentally put in the Trash,

A complete system could be restored using "Restore from Time Machine" on the DVD Installer with older versions of OS X. Since OS X 10.7, Lion, in the event of a restore being necessary, we are able to use Command + R at startup to enter an invisible partition that has the tools necessary. There is a feature in here that allows a complete restore from the Time Machine backup.

This may also be done on a computer that already has the system. Time Machine will replace all data, including settings and accounts. There are several warnings before this takes place. A warning appears to inform us that taking this step will replace all the contents of the selected volume. Note: this does mean that everything previously on the disk will be lost during the replacement process. Pressing Continue brings up a panel that shows any suitable disks available. To effect the backup, if not already in use, the disk that contains the Time Machine backup can be attached at this time.

When the disk is recognized and highlighted, pressing Continue gives a list of available backups. A full restore is likely to take a considerable time. Attaching a power supply is strongly suggested. When the process is complete the computer will restart with the restored system.

Notes

Others have been less fortunate and there are frequent tales of stolen or lost computers (same thing really), broken machines, files over-written, accidental deletions and other causes of lost data.

A backup plan is essential.

Graham K. Rogers teaches at the Faculty of Engineering, Mahidol University in Thailand. He wrote in the Bangkok Post, Database supplement on IT subjects. For the last seven years of Database he wrote a column on Apple and Macs.