Time Machine (Apple software)

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For other uses, see Time Machine.
Time Machine

Time Machine screenshot
Developed by Apple Inc.
OS Mac OS X v10.5
Genre Backup software
License Proprietary
Website Time Machine

Time Machine is a backup utility developed by Apple which is included with Mac OS X v10.5.

Contents

[edit] Overview

Time Machine, like many backup utilities, creates incremental backups of files which can be restored at a later date.[1] It allows the user to then restore the whole system, multiple files, or even a single file. It works within iWork, iLife, and several other compatible programs, making it possible to restore individual objects (e.g.: photos, contacts, calendar events) without leaving the application. According to Apple support personnel: "Time Machine is a backup utility, not an archival utility, it is not intended as offline storage. Time Machine captures the most recent state of your data on your disk. As snapshots age, they are prioritized progressively lower compared to your more recent ones."

Time Machine allows the user to back up Apple Macintosh computers through Apple's AirPort networking, but does not support backing up to normal network attached storage devices or servers. Apple's Time Capsule acts as a network storage device specifically for Time Machine backups, allowing both wired and wireless backups to the Time Capsule's internal 500GB or 1TB hard disk. Time Machine can also back up to a USB hard disk which has been connected to an AirPort Extreme Base Station after Time Machine and AirPort Updates v1.0 was released on March 19, 2008 to enable network backups. [2]

[edit] User interface

Time Machine's user interface uses Apple's Core Animation API. Upon its launch, Time Machine "floats" the active Finder or application window from the user's desktop to a backdrop depicting a galaxy and star field. Behind the current active window are stacked windows, with each window representing a snapshot of how that folder or application looked on the given date and time in the past. When toggling through the previous snapshots, the stacked windows extend backwards, giving the impression of flying through a 'time tunnel'. While paging through these "windows from the past", a previous version of the data (or presently deleted data) may be retrieved.

[edit] How It Works

When a user starts Time Machine, it creates a folder on the remote drive whose name contains the current date and time. It then copies the entire primary hard drive (except for files that it has specifically been told not to copy) to the folder. Every hour thereafter, it creates a new folder on the remote drive using the same naming scheme, but instead of making another complete copy of the primary hard drive, Time Machine instead creates hard links to files or folders that already exist on the remote drive and only backs up files that changed. (Unlike some backup utilities which save "deltas" or block level changes to a file, Time Machine will save a new copy of any changed file.) A user can browse these "versions" of the primary drive and see each file as if it were right where it was left.

While the user can browse the remote hard drive manually for missing files, Time Machine has a graphical interface which allows the user to look at a single directory, and "take it back in time". Files appear and disappear, corresponding to moments when the user created, moved, or removed them in real life. When the file the user is looking for appears, the user can select it and press a 'restore' button, which copies that version of the file to the primary hard drive. Time Machine also links to other Apple programs such as iPhoto, so photo albums can also "time travel", which is advantageous for users looking for missing pictures.

Apple system events record when each file is modified on the hard drive. This means that instead of examining each file's modification date when it is activated, Time Machine already has a list of which files to copy (the remainder being hard-linked). This differs from the approach taken by rsync and FlyBack, which need to examine modification dates first. Doing this can cause some performance issues when activated.

[edit] Requirements

Time Machine requires a non-booting hard-drive or partition to be connected to the computer or to a computer on the network, or to a network router such as an Apple AirPort Extreme, connected via a USB port and then configured to be shared with the computer running Time Machine (optional password protection may be used).[3] It can back up to internal hard-drives or partitions[4] but it is recommended that you back up to an external hard drive connected by USB or FireWire. According to Apple, it can only be backed up to network drives if they are being hosted by another computer running Leopard (including Leopard Server). Further, the volume needs to be formatted with the HFS Plus file system, with journaling enabled. If the hard drive uses a different file system type it will need to be reformatted before use, which will make any preexisting data on the disk inaccessible.

[edit] See also

[edit] References

  1. ^ Apple. Apple - Mac OS X Leopard - Features - Time Machine. Retrieved on 2007-12-21.
  2. ^ Update allows Time Machine backups on AirPort Extreme. Macworld (2008-3-20). Retrieved on 2008-05-30.
  3. ^ Tom Krazit (August 7, 2006). New Apple feature sends users back in time. CNet. Retrieved on 2006-08-07.
  4. ^ Apple. Mac OS X 10.5: Where can Time Machine back up?. Retrieved on 2008-03-11.

[edit] External links

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