iMac Cannot Restore 'Macintosh HD' to External HDD (File Too Large - Error 27)
Hi All,
Apologies in advance for the long post, but I'm in quite a predicament that's been wrecking my brain for the past 24 hours and need some help as I could potentially lose very important data.
Quick Rundown: My iMac will simply not boot from the built-in 'Macintosh HD' - I power it on, hear the chime and see the black screen with Apple Logo and Loading Bar. The Bar reaches 100% and just hangs there... forever.
Before this started happening, I did notice a severe lag in the system as a whole, and I believe it's down to either of the two things:
1) I foolishly installed "CleanMyMac X" after noticing that my iMac was slowing down and the software has obviously done more harm than good and I believe it to be the culprit as to why I can no longer boot. (I know - bad idea!)
2) My Internal HDD is possibly failing and nearing the end of its life (see iMac Specs below):
iMac 27" (Late 2013)
3.5GHZ Quad-Core Intel Core i7
24GB RAM
3TB Fusion Drive (1.97TB Used)
NVIDIA GeForce GTX 780M 4GB GDDR5
Running: macOS Mojave
I've researched this issue extensively and tried many different remedies with no luck:
- Booting in Safe Mode (doesn't Boot in Safe Mode at all)
- Resetting the PRAM
- Entering Recovery Mode & Repairing Disks
- Unplugging from the Mains, Holding Power Button for 10-15 Seconds and Plugging Back In
- This Method, although I haven't tried Verbose Mode yet (https://mrsystems.co.uk/blogs/news/too-many-corpses-being-created)
And now I've come to the following options:
- Cloning my Mac's Drive via Disk Utility to an External HDD (to save all my important data externally)
- Retrieving my Data from Backblaze (albeit there be 200 Files missing as the backup must've been interrupted from the constant slowing and crashing)
- Reformatting Everything & Reinstalling the macOS (but of course - losing everything!)
Now, I've purchased a 4TB External HDD specifically for the purpose of creating a clone of my Mac's Drive on to it. In Recovery Mode, I have formatted the Ext. HDD to MacOS Journaled and attempted to start the "Restore" process. Somewhere along the line, my Macintosh HD has become an APFS Volume (assuming it was from the Mojave update). So, when I click "Restore", Disk Utility automatically converted the Ext. HDD to APFS too so both drives match. (I think that's what it's doing when it says below 'repartitioning target device'.
This is where the problem lies... I hit "Restore" and after about 10-15 seconds I receive this error message:
"Validating target..."
"Validating source..."
"Repartitioning target device..."
"Validating sizes..."
"Could not validate sizes - File too large"
"The operation couldn't be completed. (OSStatus error 27.)
"Operation failed..."
Any ideas what I'm doing wrong here? It doesn't make sense to me that a 3TB Fusion Drive is "too large" for a 4TB External HDD - or have I misunderstood? I've tried multiple times with the same result and it's really frustrating!
I was literally in the process of preparing to back everything up after some intensive video editing work over the past couple of weeks - then this happens. (Images attached for reference):
Again sorry for the long post - but any help or advice would be greatly appreciated!
Thanks!
iMac Line (2012 and Later)