Time Machine backups suddenly no longer complete. They run very slowly only reaching ~60MB out of 21GB in ~ 1 hr. Plenty of room on external HD connected by firewire. Disk Utility finds no problem with the drive.

These instructions must be carried out as an administrator. If you have only one user account, you are the administrator.

Launch the Console application in any of the following ways:

☞ Enter the first few letters of its name into a Spotlight search. Select it in the results (it should be at the top.)

☞ In the Finder, select Go ▹ Utilities from the menu bar, or press the key combination shift-command-U. The application is in the folder that opens.

☞ Open LaunchPad and start typing the name.

The title of the Console window should be All Messages. If it isn't, select

SYSTEM LOG QUERIES ▹ All Messages

from the log list on the left. If you don't see that list, select

View ▹ Show Log List

from the menu bar at the top of the screen.

In the top right corner of the Console window, there's a search box labeled Filter. Enter the word "Starting" (without the quotes.) You should now see log messages with the words "Starting * backup," where * represents any of the words "automatic," "manual," or "standard."

Each message in the log begins with the date and time when it was entered. Note the timestamp of the last "Starting" message that corresponds to the beginning of an abnormal backup. Now

CLEAR THE WORD "Starting" FROM THE TEXT FIELD

so that all messages are showing, and scroll back in the log to the time you noted. Select the messages timestamped from then until the end of the backup, or the end of the log if that's not clear. Copy them to the Clipboard by pressing the key combination command-C. Paste into a reply to this message by pressing command-V.

If all you see are messages that contain the word "Starting," you didn't clear the text field.

The log contains a vast amount of information, almost all of which is irrelevant to solving any particular problem. When posting a log extract, be selective. Don't post more than is requested.

Please don't indiscriminately dump thousands of lines from the log into this discussion.

Please don't post screenshots of log messages—post the text.

Some private information, such as your name, may appear in the log. Anonymize before posting.

When you post the log extract, you might see an error message on the web page: "You have included content in your post that is not permitted," or "The message contains invalid characters." That's a bug in the forum software. Please post the text on Pastebin, then post a link here to the page you created.

A

Open the Time Machine preference pane and delete the backup destination. Then add it back. The backups won't be affected, although the preference pane may falsely show that you have no backups. You may have to unlock the settings by clicking the lock icon in order to do this.

B

Temporarily add the folder "Pictures" to the list of exclusions in the Time Machine preference pane. Start another backup. If it succeeds, remove the exclusion and back up again.

C

Follow these instructions to display the machine's serial number. If the number is missing or invalid according to this web form, take the machine to an Apple Store or other authorized service center to have the problem corrected.

if i can't correct C myself, is it even worth doing A and B?

C is not related to the original question, and you can't solve that problem yourself unless you're an authorized Apple technician (in which case you don't need to be told.)

i'm concerned about monkeying with my backups and possibly loosing them

As I wrote, the backups won't be affected, but it's reasonable for you to have doubts. If you don't want to take my word for it, click the "Support" link at the top of this page.