Will Formatting SSD Old Installation Effect New?

[vio1]

Hi, I have two m.2 SSD in my pc and I have an older installation of MAC OS installed on the other. I alternate between drives when I upgrade to new versions of MAC OS, because I want to ensure I have a stable installation before migrating.
My question is, if I now format the other drive, will that effect anything in my new installation? Are there any files that the new installation keeps on the other drive or am I safe to format the 2nd drive?

I would normally just pull out the 2nd drive of the computer and see if it boots up properly, but my 2nd M.2 is on the backside of my motherboard and taking it off is a large job.

 

[UtterDisbelief]

Hi, I have two m.2 SSD in my pc and I have an older installation of MAC OS installed on the other. I alternate between drives when I upgrade to new versions of MAC OS, because I want to ensure I have a stable installation before migrating.
My question is, if I now format the other drive, will that effect anything in my new installation? Are there any files that the new installation keeps on the other drive or am I safe to format the 2nd drive?

I would normally just pull out the 2nd drive of the computer and see if it boots up properly, but my 2nd M.2 is on the backside of my motherboard and taking it off is a large job.

Hi there.

You will need to know which drive has your hidden EFI partition. This is what is used to boot your PC.

It may be that you have an EFI on both, but we don't know that.

My point is you don't want to accidentally partition/format the drive your system boots from. As a precaution ensure you have a current UniBeast USB installer boot stick handy in case of emergencies.

 

[vio1]

Hi there.

You will need to know which drive has your hidden EFI partition. This is what is used to boot your PC.

It may be that you have an EFI on both, but we don't know that.

How can I determine which drive has the hidden EFI partition?

 

[UtterDisbelief]

How can I determine which drive has the hidden EFI partition?

Run Terminal command : diskutil list

This will show both drives. Check each for a 209MB (approx) EFI partition. If there are two then make a note of the disk ID and then run EFI Mounter v3.1, choose one and mount it. See if it has an EFI folder in it. Check the other.

 

[vio1]

Run Terminal command : diskutil list

This will show both drives. Check each for a 209MB (approx) EFI partition. If there are two then make a note of the disk ID and then run EFI Mounter v3.1, choose one and mount it. See if it has an EFI folder in it. Check the other.

Thanks. I did as instructed and both drives have EFI partitions and both have EFI folders. What do I do?

 

[UtterDisbelief]

Thanks. I did as instructed and both drives have EFI partitions and both have EFI folders. What do I do?

Up to you. I don't want you to loose data.

All I suggested was to discover which drive you are booting from. That was why I explained the EFI Mounter v3.1 process above, so that you could do this.

You said you wanted to upgrade one SSD but keep the other working. You wanted to know if formating one SSD might affect the other. My answer is, yes, if it is the one used to boot the system.

As I explained, check each EFI folder to find out if one or both has an EFI folder in it - which you've done. If both then you need discover which is currently being used to boot the machine. You can then make backups of the EFI folders and if the worst happens, use the UniBeast installer USB to boot your PC and restore the one you need.