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Corrupted files; Time Machine backups and other files on EHD


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Is there an app/some other automated way of checking whether there are any corrupted files in a large batch of files?  Just to make sure that all the files are in good shape after copying them to my external hard drive and so that I can safely delete them off my Mac.

Also, I've read in your past posts that you like to keep your Time Machine backups on a separate EHD from those that you use for your image files.  It made me curious -- are there any concerns with having Time Machine backups and other files on the same EHD? 

Thanks in advance!

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It’s to eliminate the possibility of Data Corruption. You do not want Time machine creating a Time Machine Backup of your Time Machine Backup Drive to itself. Clear as mud?  

Plus, what happens if that Drive fails? Not only do you lose your image files, TM files are also gone. If you say, split your external drive into two partitions, one for images and one for TM, what’s the point of using TM? The EHD is backing up to itself.

In reality, Time Machine is to backup your Primary Macintosh HD that contains the OS and programs, etc. It was never intended to backup External Drives, since they are external and should already be treated as external backups. Time Machine is meant to get you going again when your primary he fails, is replaced, and you need to restore the new one. 

Steve Jobs saw the importance of backups and wanted to make backups “fun” and “easy,” especially since the Macs were going to a sealed unit mentality; just look at how difficult it is to upgrade RAM in a 21.5” iMac or today’s modern Apple Laptops...

As far as an automated way, that’s where TM is limited. It’s not like a program such as Veritas BackupExec, which is a program that servers use, that automatically does a verify at the end of a job if you tell it to. The only way to check, is to manually check them yourself. Honestly, all verification does is check the file size and extension and see if things match. BackupExec never opens the file, just makes sure the file could be read and is the same size / extension as the original. 

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Whoops, sorry, I think I wasn't clear on that first question.  Or I don't understand your reply...?

For background: my Mac laptop has 1TB SATA drive.  Not all my image files will fit on it, so I have three EHDs that have TM backups of my Mac (two 1TB, one 2TB in capacity), as well as three EHDs that has all the image files that don't fit on my Mac (all three EHDs are 1TB in capacity).  These three sets allow me to have one backup at home and two offsite.

The only thing is...the 1TB EHDS are all nearly full.  And the 1TB internal HD on my Mac has only 150GB left of capacity too.  So I nearly had a heart attack when I read the rule in your previous posts that the EHDs and the internal HD on the Mac should be only at 65% capacity.  (YIKES I had no idea!)

So to fix my problem, I've bought two 5TB EHDs.  Ideally I'd like to keep doing the three sets of backups thing.  That means that I would have (I was thinking):

- two 5TB EHDs that have a TM backup and the image files that don't live on my Mac

- one 2TB EHD that has the image files that don't live on my Mac

- one 1TB EHD that has a TM backup

(And I'll clean up the Mac so that the TM backups are within the reasonable limit!)

So I'm not really backing up the EHD to itself...I can see that happening if you have all your image files living on your Mac, and then, copying those same image files is redundant.

Crikey, I hope I've explained myself.  Apologies if I haven't!  Clear as mud indeed??

And thanks for the info about the verification -- there's no way to do all of them of course, so I generally just check a few files (that they'll open with no problems) and be done with it.


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Oh!! Now I get it!! Now that’s a better question. Actually, you don’t want to go above 80% full on ANY Mac HD, internal or external. I usually state  a conservative number, like 75% to give members a bit of wiggle-room. As soon as you go above 90% full, things can get serious in a bad way...95% or more...downright scary and dangerous. You are really playing with Fire above 95% full.

The reason is, the Mac OS treats both internal and external hard drives the same. (I won’t go into specifics of why, your eyes will glaze over, LOL!) So if you are full on your main drive, you will have a performance hit, if one of your externals is full, you will have a performance hit. So the fuller the HD, the slower a Mac runs. The more files / folders / crap stored on the Desktop, the slower the damn thing runs.

Here is what I would do: Use your 2TB drive for TM only. Even if you reformat it and start over. Put nothing else on it. Your 5TB drives take the place of your two 1TB externals. Move the existing data / image files to two separate main folders, one labeled 1TB EHD 1 & 1TB EHD 2, unless the drives are just duplicates of each other. Then all you have to worry about is one EHD and one folder. 

Going forward,  you can duplicate one of the 5TB drives weekly and keep it off-site. I would not let TM manage backing up your externals, YOU need to do that. Only have images / data on the 5TB EHDs. In the long run, you are keeping things simple. If you ever had a catastrophic failure, putting all your eggs one one basket with TM isn’t a good idea. TM is really meant for your internal HD only. Not your other externals. So says me. And the Apple Employees that work at the Genius Bar. ;) 

For your main drive: CULL-CULL-CULL!!! 

You do not need 75 photos of your lunch taken 5 years ago. Those out of focus images from that family session 3 years ago and will never see the light-of-day? GONE!! 


Your goal is to get above 350GB free on your internal Mac Laptop HD. Better yet, shoot for 400GB. Even if you have to move some items temporarily to one of the 1TB drives as a place holder. 

While you are at it, now is a good time to review how your file / folder structure is laid out. Does it work for you? Can you find things within 30 seconds? Or is crap all over the place? Now is the time to make things better...while culling, organize things. 

I’m sure this is going to take a week or so, but keep chipping away at it. When it’s done, your Mac will be in a much better place. Right now, I’m a little concerned. 

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Hi again...finally LOL!

It is done.  Ha, that turned into a marathon, eh? Busy summer turned a week's work into three.

Thank you again for the information and advice -- I now have all my images on those two 5TB EHDs, which freed up my Mac to 630 GB of 1TB free :D

And I also have two Time Machine backups...I was hoping for a third but that 8 year old EHD bit the dust.  I'll get another 2TB EHD when cash flow is more optimistic than it is presently, so the two for now will do.

Cheers! Carmen

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