Q I used to leave my external FireWire drive running and mounted to store Time Machine backups, but it proved impossible to eject and I had to switch it off or pull the FireWire cable before I could shut the iMac down. I have been told that this was caused by Spotlight trying to index the backup, and that I should place a hidden file named ‘.noindex’ on the backup to fix it. Is that correct?

A It is easy to tell whether this trick, to turn off Spotlight indexing, is likely to help. Immediately after you experience problems ejecting the external drive, take a look in the logs using Console. If indexing is running into problems, you should see a stream of messages referring to mdworker (the indexing daemon) or the metadata server itself, mds.

Most who use Time Machine put their backup volume on the list of items which Spotlight is not to index. This is because the backup contains so many files that its indexing can cause problems like this. The disadvantage is that Spotlight searches do not then access your backups, but given the multiple copies of many documents there, that is perhaps not a bad thing after all.

The simplest way to exclude your backup from Time Machine is to open its pane, click the Options… button, then add the backup folder or volume to the list of exclusions, by clicking the + button. Then click Save.

Details of other methods are given here.

Comments Avoid turning drives off or pulling a cable on them in this way, as it is almost certain to cause damage to them. Before doing anything else you should carefully repair that drive using Disk Utility, as errors on the drive can themselves cause this type of problem. If you have to shut down quickly, hold the power button to force a shutdown instead.

Updated from the original, which was first published in MacUser volume 28 issue 17, 2012.