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First time posting, also a Mac newbie (recent windows convert) so I'm hoping I can get some help here :)

I have a Hitachi Deskstar drive in an external casing that I got from ebuyer. (its one of those unknown fairly cheapish enclosures) connected via firewire.

I hook it up and it works fine, but then at some point over the next week or so I'll realise that my last update was 3 days ago or so.

At this point the Mac will not recognise the drive as existing and the only thing to do is switch off and on the external enclosure.

It then works fine for a while.

If I had to guess I'm assuming its powering down or something when the Mac goes into standby? Is there anyway to solve this?

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Time Machine stops the backup if the Mac goes to sleep. Time Machine does not prevent sleep however nothing will be damaged if the backup is interrupted. TM will just resume backup after you wake the Mac back up. So even your disk power does down, time machine backup should just stop end continue after disk is on line. Your external hard drive is formatted as mac journaled, other way time Machine doesn't work. Usual time machine schedule is every hour interval backup. If schedule passed whatever reason, the time machine start next closest hour backup automatically.

Points to check:

  1. Check console errors messages Way- Mac HDD-Applications-Utilities
  2. Check the drive permissions fix. Drive Utility (Utilities folder)
  3. IF doesn't helps. Reformat your drive with MAC Journaled (!LOST ALL PREVIOUS BACKUPS!) But It seems to me you already answer your question yourself: ...(its one of those unknown fairly cheapish enclosures) connected via firewire...
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Need more information: Is the drive not remounting after your machine wakes up? If you're not noticing it, maybe it will help to display it on the desktop: Finder -> Preferences (command+,) -> General -> Show External disks on the desktop. This way, you can see at a glance which drives are mounted at any given time.

Time machine won't work if the drive is not mounted. It should be coming back up when your computer wakes from sleep, but if it's not my guess would be that it's a problem with your no-name enclosure. I would add the make and model, even if its not a well-known brand, to your question so we have the specifics. It would be good to know if the manufacturer fully supports Mac, and if the chipset is the same as a more widely-known enclosure.

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