Ejecting TM HD: error code -36

Question

I've been experiencing problems that appear to be related to time machine for several months. I used to leave time machine on 24/7, and most of the time I would leave my mac on 24/7 with periodic reboots and ~weekly shutdowns. But then Time Machine started hanging during the "Preparing backup" stage. I mean, it would just sit there and spin for hours. I would leave it on overnight and I would come back in the morning and it would still be "Preparing backup." It would not respond to "Stop backing up" requests, and when I would try to retrieve a backed up version, TM would hang, and everything would be completely unresponsive (no way to force a shut down of TM) until I shut off (or unplugged) my ext HD. I've had a recurring specific problem with files being deleted related to Dreamweaver CS3, that only happens after TM hangs and I have to d/c the HD and then OS hangs when I try to reboot (or shutdown) and I have to hold the power button down to force a shutdown.
So, recently I've begun only turning on and connecting my ext HD once or twice a day, to make sure I get some good backups, and this seems to be a way around the TM hang issue. But just today, after I got a good backup, I tried to eject the ext HD and I get an unexpected error code -36. What is going on? I can't help but get the feeling that this is related to that OS update that ran yesterday. Is anyone else having this sort of issue? Any ideas to solve it?

Answer 1

macographer,
Try to avoid "forced restarts" as much as possible. If you must stop a backup, then use either “Stop Backing Up” from the Time Machine menu, or click the tiny "x" icon in the Time Machine preference pane. Both procedures will work and should not be considered a dangerous interruption. [http://docs.info.apple.com/article.html?path=Mac/10.5/en/15144.html]
As for extended sessions of preparing, see the article below.
*_Time Machine May Report "Preparing..." For a Long Time_*
First, it’s good to determine WHY Time Machine is "Preparing..." for an extended period of time. Examining the Console logs during this event can reveal what is actually going on behind the scenes. It may be “Preparing…” for a genuinely good reason. How long is 'too long' to wait for Time Machine to finish "Preparing..."? Some times, "Preparing..." is required to perform the normal housekeeping that Time Machine does periodically. Other times, it really is "stuck" and never proceeds after more than 24 hours.
*”Deep Traversal” (Recent Crash / Forced Restart / System Update / Extended Period Between Backups)*
According to the following KB article it can sometimes take quite a long time if Time Machine begins a “deep traversal” and has to compare data inventories. This may apply to your situation, particularly if many Gigs of data are involved. [http://support.apple.com/kb/TS1516]
You see, Time Machine *+does not+* ordinarily perform file-by-file comparisons to determine what has changed and thus determine what needs to be backed up. Rather, Time Machine relies on FSEvents notifications. This is a log that the system uses to keep track of changes to directories. Rather than scan tens of thousands of files for changes each time, Time Machine simply looks at this log and narrows its’ scan to only the directories that have experienced changes since the last backup. Otherwise, Time Machine would have to be running constantly just to catch every change on its own and thus eat up precious CPU.
Every event that FSEvents records has its’ own ID which includes a time stamp. At the end of every backup, Time Machine stores the last event ID that it processes. When the next backup is initiated, Time Machine looks at this stored ID and determines that it only needs to backup events that have occurred after the time stamp on this last event ID.
If, due to a system crash, power failure, forced restart, or some other major system event, Time Machine cannot find this last event ID in the system logs then it will consider the FSEvents log “untrustable” and it will go into what’s called “deep traversal”. The Console logs may report +“Event store UUIDs don't match”.+ In this event, Time Machine will by-pass the system log entirely and perform its’ own file-by-file comparison to determine what has changed since its’ last backup. Obviously, if tens or hundreds of Gigs are involved, then this process can take quite some time and should be allowed to proceed.
Additionally, it appears that if Time Machine has to go back too far to find the last event ID, then it will give up and simply go into “deep traversal” and do the file-by-file scan on its’ own. This can occur if Time Machine has not been able to perform its’ hourly backups for some time, as is the case for users who only backup once a week or so. This is also the case with major Mac OS system updates that change thousands of files at one time. There are simply too many events logged by the system for Time Machine to bother looking for the last known event ID.
*Anti-Virus Software*
Running anti-virus software can interfere with the backup process. Either disable it altogether, or try the suggestion outlined here, “If you use third-party anti-virus scanning software and have issues, make sure your Time Machine back up folder (Backups.backupdb on the Time Machine disk) is excluded from virus scanning.” (http://support.apple.com/kb/TS1516)
*Software Updates* #
Installing new software, upgrading existing software, or updating Mac OS X system software can create major changes in the structure of your Macs directories. Time Machine will backup every file that has changed since the installation.
After an OS update (like 10.5.5) Time Machine realizes the system no longer matches what it looked like during the previous backup. So it has determined that it's earlier catalogue of what-should-be-where is “untrustable”. So it is going to go item-by-item comparing the before and after of your system. If you have just performed an OS Update then Time Machine knows what it's doing - let it do it!
*Spotlight Keeps Indexing Backup Drive* #
It may be that Time Machine can’t proceed or complete a backup due to a Spotlight indexing error. During this period, take a look at the Spotlight icon in the upper right corner of your screen. Is there a tiny dot pulsating in the center of the spyglass? Click on the icon. Is there a progress bar displayed? Generally, Spotlight indexing is a good thing. If it has only been a couple of hours then let the process continue.
However, at times it may hang and never progress after many hours, preventing further backups from taking place.
Go to System Prefs --> Spotlight --> Privacy Tab.
Drag your Time Machine disk into the window. It should now be among the items to exclude from indexing.
Now quit System Prefs.
Reboot your Mac.
Reopen System Prefs and remove ("-") the Time Machine disk from the window.
Now initiate a backup.
This should clear out Spotlights cache. Naturally, Spotlight should begin indexing again (maybe even for a few hours depending on how much data there is), but it should eventually stop.
*Run Away System Process*
It’s possible that Time Machine is stuck “Preparing…” because another process is monopolizing your Macs’ CPU. Launch Activity Monitor and sort the items by “CPU”. Is there a process that is at or near 100% that might be preventing the backupd process from moving forward?
One poster stated, “I took it to my local Genius Bar and they found a Syslogd daemon running, taking up 100% of my CPU. The result (other than bad performance) was that the disk configuration was constantly dynamic, thus TM could never pin it down to back it up. This resulted in the "Preparing..." mode running forever. They resolved it by simply reloading the OS X to 10.5.4. It ran fine on that and I've now updated back to 10.5.5 and everything is running fine.” [http://discussions.apple.com/thread.jspa?threadID=1755600&tstart=15]
You can use Activity Monitor to “kill” the offending process. Or you may be able to resolve it simply by rebooting your Mac. Then try backing up again.
*Verify/Repair Mac Hard Disk & Permissions*
It may be that your Macs’ internal hard disk has so many file/directory issues that Time Machine simply has trouble making sense of it. Some users have had success using Disk Utility on their Macs’ hard drive.
Launch Disk Utility and click “Repair Disk Permissions”.
Once complete, attempt a backup.
If Time Machine appears to hang at “Preparing…” again, then do the following:
Insert your Macs’ original install DVD and reboot holding down the “C” key.
At the Welcome screen go up to the “Utilities” menu and select Disk Utility.
Select your Macs’ hard disk on the left and click “Verify Disk” on the right.
If problems are found click “Repair Disk”.
Reboot to your normal desktop and try backing up again.
Let us know if any of the above was helpful in your case.
Glenn
Message was edited by: Glenn Carter
Message was edited by: Glenn Carter