Posted by: Chris Barylick
Date: Tuesday, April 14th, 2009, 09:23
Let’s face it, Time Machine is a spiffy and useful thing as well as one of the main bells and whistles of Mac OS X 10.5. This isn’t to say it’s without its bugs and despite Apple’s best efforts, there are times where backups appear to hang or stall out sans warning.
You may be familiar with the situation, as described by poster “PaulArthurUK” in the Apple Discussion forums:
“When time machine starts to back up my machine, it hangs (the clock icon in the top right-hand corner of the screen spins, but the backup disk is not being accessed and currently Time Machine shows no backup in the last five days). Once it has hung, various applications start to behave oddly and generally I am unable to shut them down, even via force quit.”
Per MacFixIt, there are a variety of reasons why this could happen. The most common is when the backup daemon is doing a “Deep Traversal” of the source drive to ensure its catalog of changed files correctly reflects the status of the source disk. When this happens, Time Machine will stick at “Preparing…,”. This can take a long time, depending on the size of the node being traversed, but usually speeds up once the deep traversal is completed.
To easily check out Time Machine logs and track down problems and exactly what Time Machine is doing, download the “Time Machine Buddy” widget, which will display the TM logs in the dashboard.
Time Machine’s hanging may affect other chunks of the operating system, causing widespread slowdown. This type of behavior usually indicates the system resources are not accessible to the system when the system is expecting them to be.
Other scenarios that may cause a slowdown include the following:
Drive malfunction: If the drive is making clicking sounds, or doesn’t appear properly either on the Desktop or in Disk Utility, then there may be a problem with the drive. For external drives, low power to the drive can cause the system to hang.
Volume corruption: While the disk may be fine, if the formatting or partitioning of the drive has problems, then the drive will not be properly accessible by the system.
Drives being put to sleep: The energy-saver setting to put drives to sleep whenever possible can cause them to go into a state where they won’t wake up properly. This depends on the drive itself, but while the system waits for the drive, you can experience a hang.
User can try running Disk Utility to check for and repair errors on the drive or perform these tasks more thoroughly with a third-party disk utility software such as “Disk Warrior,” “Drive Genius,” “Disk Tools Pro,” or “Tech Tool Pro.” Checking both the boot drive and the Time Machine drive for errors is recommended.
Beyond drive-specific issues, there can be incompatibilities both with other system resources and third-party applications, which can cause Time Machine slowdowns. Antiviral software can interfere with Time Machine’s functions, especially if you have live scanning or “on-access” scanning enabled. Turning off these settings in the antivirus software may help this situation. Additionally, if you have Spotlight enabled for the Time Machine drive (it is enabled by default), this can sometimes endlessly try to index the drive. As such, you can try adding the Time Machine drive to Spotlight’s privacy list, and then remove it to restart indexing.
A similar trick can also be performed via Mac OS X’s Terminal application, which will ensure the spotlight stores are deleted and started anew via the following steps:
Type the following command and include a space after the command:
mdutil -E -i off
Drag the Time Machine disk to the Terminal window to enter the full path to the disk, such as the following:
mdutil -E -i off /Volumes/TMDisk/
Ensuring a space is between the “off” and the drive path, press enter
Repeat this command, changing the “off” to “on” in order to enable spotlight on the drive again.
Finally, if you are backing up over a network (especially a wireless network), backups can be slow by nature. At 54Mb, speeds of most wireless connections, you will run at a maximum of 6MB per second, which translates to 14 hours for a 300GB backup when running at optimal conditions. Given network overhead and other interferences, this can easily double and result in the backup taking a day or two. For the initial backup to a networked device, you might try plugging in the Ethernet connection, which should be at least double the speed, but up to 20 times faster than wireless.
A final fix for slow backups can be to restart Time Machine on the drive by removing it and re-adding it in the Time Machine preferences. Doing this seems to clear various bottlenecks in Time Machine and start backups running at faster speeds again.