Local Snapshots in Mac OS X Lion Time Machine: Is It A Good Idea?

Apple is readying the next major release of their Mac OS X operating system. Dubbed “Lion”, Mac OS X 10.7 is widely expected to hit Apple stores in the Summer of 2011, and brings many exciting new features along for the ride. This series of articles introduces the storage and data protection features of Lion as they are revealed.

Many operating systems include a backup client, but not many are as widely-used as Time Machine in Apple’s Mac OS X. Time Machine presents an extremely simple interface for data protection, making backups literally a one click task. Until the release of Lion, Time Machine required the use of the second hard disk drive, often an external USB or Apple network attached unit. In 10.7, Time Machine gains the ability to use the local primary hard disk drive to store snapshots of files. Is this really a good idea?

What are you protecting against?

One reason so many people are dissatisfied with their backup solution is that they use it for too many conflicting purposes. They expect the same application to provide short-term file recovery, bare metal restore in the event of a hard disk crash, long-term retention of data, and even off-site disaster recovery.

Most back of applications, including Time Machine, are very good when it comes to short-term file recovery but fall short in answering these other demands. A “best-of-breed” solution requires a number of different applications for end users or a pile of money for their enterprise counterparts.

The real innovation of Time Machine was it ease-of-use: When a user attached and external hard drive, Mac OS X asked for permission to use it as a backup target and automatically configured all other aspects of the system. File recovery is done in a very user-friendly way, with a Cover Flow like interface to move forward and backward through different versions of the folder.

But Time Machine requires a second hard disk drive, and very few Macs ship from Apple in this configuration. Although paired storage is becoming more common, the majority of MacBooks and iMacs ship with a single internal hard disk drive. Until the end user purchases and connects their own external drive, these systems would be unprotected.

Introducing Time Machine local snapshots

Mac OS X 10.7 “Lion” introduces a number of storage enhancements, including the ability to track versions of files in Finder. Time Machine gets a similar function, storing local versions of files in addition to standard backups on an extra drive.

It is not at all clear if Time Machine’s local snapshots capability leverages the “Versions” feature or simply stores files locally the same way it does on an external drive. But the end result is the same: Users will be able to protect their data even when no external drive is attached.

There are serious drawbacks to this approach, however. Storing backup data on the same hard disk drive does not protect from the loss or failure of that device, and hard disk crashes are fairly common, especially in portable devices. This could also present security concerns, since a laptop using Time Machine local snapshots would store confidential data locally long after it is deleted.

Clearly, Apple realizes the limitations of this strategy, and will still recommend using an external drive for Time Machine backups. But it is better to have a local copy of data than none at all, and Time Machine local snapshots will likely be a boon to the average MacBook user.

Stephen’s stance

Although it is not a full-featured backup application, I heartily endorse Time Machine since its ease-of-use encourages average users to backup their data and enables them to recover lost files in a user-friendly environment. Time Machine local snapshots add another layer of protection for Apple users on the go. As long as they do not rely on local snapshots exclusively for data protection, I call that a win.

I wonder whether end-users that have experienced Time Machine are more or less likely to deploy a real backup application or an off-site backup service like Mozy or Crashplan. Perhaps Time Machine piques their interest in data protection, causing them to go out and purchase such a service. A multilayered approach with Time Machine local snapshots and external storage plus an online backup service is light years beyond the data protection enjoyed by average users.