7 Replies Latest reply: Mar 11, 2011 3:34 PM by Will Mardis
Will Mardis Level 2 Level 2
On 2 recent occasions, the Time Machine partition on my network attached storage device (a 3rd party unit, not Apple) became inaccessible after a power failure. The only way to make the unit functional was to restore it to its original configuration which meant losing all the data on the unit. So, what good is a backup unit if it fails under conditions that might be expected to cause problems with my computers' hard drives (btw, I've never lost saved data from my Mac computers as a result of a power failure.)

My questions are: is this behavior (losing Time Machine data as a result of a power failure) to be expected? And, does anyone have experience with Time Capsule to suggest that I would not experience the same issues if I upgrade to Time Capsule? Will Time Machine data on a Time Capsule still be accessible after a power failure?

Thanks in advance for all assistance on this.

Quicksilver DP 1 GHz, 15 PowerBook, MacBook, Mac OS X (10.5.8)
Reply by macjack on Sep 22, 2010 7:13 AM Helpful
Yes, and Power failures can do worse than that. Your MacBook has the battery to switch over to, your external disk has no protection built-in. It would need to be connected to a UPS (Uninterruptible Power Supply). If you have any desktop Macs, you've been very lucky, They should be on UPS too.This is a battery backup unit that will ensure when there is a power outage, it instantaneously kicks over to backup so power remains constant to your Mac, or drive until you can shut down normally or program it to do so. This is a link to APC one reliable maker of such equipment. You can click through and use their wizard to find the one that's best for your specs. -mj

All replies

  • macjack Level 9 Level 9
    Yes, and Power failures can do worse than that. Your MacBook has the battery to switch over to, your external disk has no protection built-in. It would need to be connected to a UPS (Uninterruptible Power Supply). If you have any desktop Macs, you've been very lucky, They should be on UPS too.

    This is a battery backup unit that will ensure when there is a power outage, it instantaneously kicks over to backup so power remains constant to your Mac, or drive until you can shut down normally or program it to do so.

    This is a link to APC one reliable maker of such equipment. You can click through and use their wizard to find the one that's best for your specs.



    -mj
  • Pondini Level 8 Level 8
    Will Mardis wrote:
    On 2 recent occasions, the Time Machine partition on my network attached storage device (a 3rd party unit, not Apple) became inaccessible after a power failure.


    Can you see the +sparse bundle+ your backups are on via the Finder? If so, you might be able to repair them, per the instructions for a Time Capsule in #A5 of Time Machine - Troubleshooting (or use the link in *User Tips* at the top of this forum).

    If not, does the maker of the NAS have any sort of disk/directory repair options?
  • Will Mardis Level 2 Level 2
    Nope. Maybe if I knew the volume name and password, but they appear to have been changed and/or corrupted as a result of the power failure.

    Fortunately, all my data on the 2 computers I'm backing up is still intact. I've now returned that 3rd party NASD and replaced it with an Apple Time Capsule. So far, it's working BEAUTIFULLY!!
  • Pondini Level 8 Level 8
    Great!

    But a Time Capsule is subject to power problems, too. Usually the file system on them can be repaired after a power loss, but if you have frequent power outages (or spikes or brownouts), consider getting a U.P.S. system for your TC (and modem, etc.).
  • chownsb Level 1 Level 1
    I've now had this happen twice in only a few months with an external USB drive. After a power outage my Time Machine backups start "processing" millions of files (endless). Running Disk Utility tells me the volume can't be repaired and that I should copy as much data as possible from it, at which point it is no longer mountable.

    My drive is split in half and the other partition always survives just fine. It seems something to do with the Time Machine partition is susceptible to corruption. A backup system that can't survive a power outage isn't one that I'll ever put much trust in. Time Machine was not even enabled when the power went out.
  • chownsb Level 1 Level 1
    I found a useful bit of information for fixing this problem here: http://blog.jthon.com/?p=31

    In my case, all I had to do was run "fsck_hfs /dev/disk1s2" and wait. Apparently running Disk Utility doesn't do a full fsck and doing so manually can yield better results. If you're using a Time Capsule I think you need to follow all the instructions on the linked site.

    An easy way to find out what device ID your partition has is to open Disk Utility, right click the partition, and click "Information."
  • Will Mardis Level 2 Level 2
    Solved my problem by replacing third party backup drive with a Time Capsule. I've experienced several power outages since doing so, and have not lost any data.

    Apple, you make GREAT stuff!