Another Clone HD Thread - A Mac User

I’m upgrading/downsizing from a fullsize external (with power supply) 3TB drive to the WD Elements 2TB drive.

Now I don’t want to try and watch everything before I do the switch so searching this site i’ve seen some threads on successes of doing a drive clone. But most people are using windows - I have a MAC

What I’m currently in the process of is using dd in OSX’s terminal to do a bit level clone. By plugging in the current HD OSX states that it can’t read the drive, but I just ignored that. I also first plugged in the new drive to the tablo so it was formatted but nothing recorded, then hooked it to the Mac

It’s been running dd for about 12 hours, but I have no prior experience with dd so I don’t know how long it will take. The existing 3TB HD only had roughly 500GB used. So no idea if it has to go over the whole thing or just what’s been used. Also of course they are both connected by USB.

Anyone have any experience with dd clones of a HD in OSX??

Most of us went small to large. Mine ran over 24 hours then windows closed it because of not enough memory. I lived with it and lost a few episodes of Adam 12.4

I am a Mac person also, but don’t know how to do this, but would like to know if it works for you. I don’t really know much about terminal. I would like to go to a larger drive but move over about 1TB. Hope you figure this out.

I’ve read a lot about this…the key will be to see if going larger to smaller will work or not. The interwebs seem to be conflicted in this regard. Some say it will work so long as the larger is not completly full and I’ll have to resize/fix the partition because of the size difference.

however going from smaller to larger shouldn’t be an issue. @sodaman_2000 check out this is what I referenced… I’m making the assumption that even though the OS can’t read/write the ext format of the drives tablo uses that dd being a bit level copy won’t have an issue with that and still copy it. We will see.

Mine has been running for about 15 hours and is still running (based on the HD lights still flashing). I’m hoping it finishes before tonight so I can boot up the tablo before it needs to record.

You might be best off using a Gparted boot CD / thumb on your mac … this is probably the best/safest way to “downsize” since dd would only work as you are using it on a 1 to 1 clone … any resizing needs the resizefs command (linux) to adjust the partition tables … gParted handles this for you … make a gparted bootable CD or USB drive and boot your mac into gParted (if using a burned CD hold down the C key while booting your mac with the cd in the drive… or you can hold down the Option key instead to choose from available bootable devices currently attached)

the reason your mac doesnt recognize the disk is it needs a 3rd part filesystem plugin eg…ExtFS to be able to read/write to EXT formatted disks.

(I am a Mac user myself and have extensive Linux and Windows experience)

I actually saw this after I started the dd, but figured I’d let it run and see what happens.

So are you saying I can create a bootable/live cd of gParted and it will clone the larger 3TB drive to the smaller 2TB drive and fix the partition issue all at the same time?

Pretty much yes assuming you dont have more than the capacity of the target drive on the source drive…

ok sweet - if it’s still running tonight I’ll kill it (since its probably not going to work)…and try this. Yeah my 3TB drive is not using more than 1TB…I don’t think its more than 500GB used.

Please be sure to read up on gParted because it could cause hard drive corruption if its not used correctly… or accidentally and it would be rather difficult to recover from … (you’d need to restore your machine from your timemachine backup in the worst-case scenario … eg you accidentally wipe your mac’s internal harddrive by mistake)

I’m taking a read now - I’ve used gParted before it’s just been a long time since I had a Linux box and/or had the need to do this type of work. And I didn’t know you could live boot it.

Looks pretty straightforward - so long as I have to source and destination properly picked and to stay away from the Mac’s HD (but I have plenty of time machine backups either way on my NAS).

for what its worth I used a virtual machine because I am lazy… and it worked fine that way too.

similarly I’m to lazy to create a VM… :slightly_smiling:

technically neither did I … I just booted off the iso file … (yup im that lazy)…

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Just in case someone with a Mac that stumbles on this…below are the steps that I followed that so far seem to work.

The terminal route with the dd command may have worked but in 24 hours it had only copied 1.5TB (it does a full disk copy even if it’s blank). So I killed it. It wasn’t likely to work, or the finished product would be corrupt since the target drive is smaller than the source.

Below is the steps I took that seem to be working thus far without issue:

  1. Download and create a bootable CD/USB of

  2. Boot your Mac to gParted - I used a CD so I just held the “C” key down when it is booting - you’ll hear the CD drive spin up and you won’t see the typical Mac boot screen. Here are the key’s for boot options in OS X - Have both drives connected to your machine when booting (not sure if this is crucial or not)

  3. gParted takes a while to boot up so be patient, probably faster from USB (but I only had 2 USB ports and needed both for the drives). It will see all your drives and you can switch between them in the top right. Make sure you know which one is your Mac’s HD - you don’t want to mess with that one. I could tell based on the sizes of the 3 drives that were connected.

  4. If your going from a larger drive to a smaller drive like I was, you have to re-size the partition on your larger (current) drive to something equal or less than your new target drive or it won’t let you copy/paste (next steps). This won’t lose any data so long as your drive isn’t completely full. If it is full then this won’t work (going from larger to smaller). If your going from a smaller to larger drive, then you shouldn’t need to re-size your partition. You do the re-sizing by selecting the appropriate drive partition and clicking the re-size button, move the slider, click OK, and then apply, then wait for completion.

  5. Switch to your new target drive and create a partition, click new, accept the default values as I believe the next steps will overwrite any of these anyway. Click apply, then wait for completion.

  6. Now switch back to your current original drive and click the partition, and click the copy button.

  7. Switch to the new drive, click the partition, click paste, click apply, walk away and come back in a few hours…wait for the completion message.

  8. Plug the new drive into the powered down Tablo…power it up, and you should be off and running like nothing changed.

–I was moving from a 3TB full sized desktop drive (3.5") to a 2TB Western Digital Elements drive. My 3TB only had used about 300GB of space. This process took around 4-6 hours. I was also doing this via a 2009 MacBook Pro with both drives connected with USB. It’d probably be faster with newer hardware.

–I confirmed within the Tablo settings page that the new drive size was detected, I also confirmed by opening/watching 2 - 3 recordings (the first few min) that everything was still there. Since my drive is nowhere filled up, I don’t know if any of the re-sizing of the partitions will have any negative affect on it. I wouldn’t think so, but only time will tell - I doubt I’ll ever come close to filling up 2 TB to know either (I have a 20HR Tivo HD that we don’t even fill).

–I re-sized the original larger drive back to its full capacity when I finished…but this took a very long time since it was a 3TB drive. I didn’t just want to pull the cable on the new drive (since that one was done) so I had to wait until that re-size was done to hook it back to the tablo. I recommend re-sizing the now old HD after you confirm the new one works. Or don’t do it at all.