Running 2012 MBP and MBA off same external USB3 SSD. Comments?

[minvoyager]

I have a mid 2012 MacBook Pro 15", and a mid 2012 MacBook Air 11".

Rather than upgrading the internal SSDs, I'm contemplating having an external SSD in an enclosure, where I can boot MacOS Sierra off the external SSD for either the MBP or MBA (not at the same time, of course). Both have 8GB RAM.

I'd like to hear the experience of others who have booted a 2012-era MBP or MBA off an external SSD in an USB 3.0 enclosure.

I anticipate it will give slower performance compared to an internally-installed SSD, but if the performance off the external SSD is acceptable for daily use (email, browsing websites), then I could accept that.

Is that technically feasible -- to boot the same external SSD off two different Macs?

I read a recommendation that, rather than using cheap USB 3.0 enclosures, it suggested a Vantec NexStar. So I'd use that.

 

[New_Mac_Smell]

Is there a reason you specifically want to use 1 SSD for both? A decent external drive that would be fast enough is likely to cost about the same as 2 internal SSDs, or near enough to warrant forgoing all the hassle. You'd be best with a thunderbolt 2 over USB due to TRIM support too. https://forums.macrumors.com/threads/external-ssd-as-boot-drive-usb-3-vs-thunderbolt.1709803/.

In terms of running 2 machine from a single shared source I'm unsure, I'd hazard a guess at no but I'm not familiar with how MacOS works at that level, hopefully someone can Google it or tell you.

Why don't you just upgrade the SSD in the Air and sell the Pro? If it's just for light browsing, it would seem silly to have 2 computers for it. It also wouldn't be particularly portable, so why are you wanting to keep 2 machines in a hindered way when you could use 1 more freely?

 

[minvoyager]

Is there a reason you specifically want to use 1 SSD for both?

Why don't you just upgrade the SSD in the Air and sell the Pro?

I need to have two Macs, one as a backup. But the files are the same files. Hence, if I can run the same SSD connected to either of the Macs (MBP, MBA) then that would suit my purposes.

 

[New_Mac_Smell]

I need to have two Macs, one as a backup. But the files are the same files. Hence, if I can run the same SSD connected to either of the Macs (MBP, MBA) then that would suit my purposes.

That seems a really bad idea for a backup. What if (As is more likely) the SSD is the thing that gets damaged, with the fact it's portable and so movable?

You'd be far far better off upgrading the SSD, and getting a cheap external drive as a backup. And then worst case you need that 2nd backup Mac, you have backed up data. The data is the most crucial thing on a computer, not the computer itself.

 

[Fishrrman]

Let each Mac "be its own Mac".

If there are files you need to share between them, you could keep the files themselves on an intermediary drive or USB flashdrive.
(But you'd better keep that intermediary drive backed up!)

I would designate ONE MacBook (the Pro?) as the "primary" computer, the other as a "secondary" one.
All the important data resides on the primary computer.

In fact, that's how I do things myself, between -3- Macs.
The one I'm typing on now is the primary Mac.
The other two are "non-primary", and they never see the files that are on this one.

 

[jerryk]

The question I have is that even technically feasible. No doubt there are plists and other files that get configured for system A. If you take this over System B do these work? And what if the device referenced is not present on the other system?

I can see doing it for data drive, but am interested to know if this works for the system drive.

 

[ZapNZs]

Could you describe your usage a bit more that is leading you in this direction?


My knowledge in this area is limited, so bear with me (and feel free to correct me if I have said something incorrect.)

It is technically feasible in that system drives on one Mac can be ran on another (provided the OS revision is supported on both systems) but it may be much, much slower depending upon the SSD and the lack of TRIM (I've had some system drives slow on me considerably in write speeds when TRIM was disabled in the past). There is also the concern of what could happen to data on the drive should it be accidentally removed during operation (especially during write operations if the SSD lacks any form of power loss protection.) If you use a SSD in this fashion, IMO backing up this SSD on a frequent basis to a secondary physical SSD or HDD using a cloning program (and not Time Machine) would be absolutely essential - this may reduce the convenience by increasing the work you have to do.

I am not sure how certain licensed programs would work that use more than just the local hard drive for identification with hardware-locked licensing.

In my personal opinion, I think there are potentially better solutions worth exploring, such as using the internal SSDs as your system drives, and using an external SSD as your data drive (and backing it up since SSDs fail also.) Also, NAS may be of interest? NAS, IMO, offers a much more convenient solution, with more options for redundancy in the case of disk failure, with less work the User must perform to achieve this after initial configuration.

The Vantac Nexstar is a product line that I believe offers a variety of interfaces, including USB 3.1 gen 1 (3.0) type-A, USB 3.1 type-C, eSATA, and formally FireWire 400/800. In the case of USB, the chipset used with the SATA bridge can have an effect on performance and the chipsets chosen vary by brand, tier, and specific model - as of 2017, most modern enclosures seem to support UASP. For housing OS' (and using external SSDs in-general), I've personally found ThunderBolt and eSATA to be better than USB. YMMV.

 

[minvoyager]

The reason for this strategy is that I have important legacy software that can only run on Mountain Lion, so I wanted to keep the ML OS on the main drives of both the MBP and MBA, and then use the external SSD to run the latest macOS Sierra and later High Sierra.

I use the legacy software often enough such that I wish to keep the MBP and MBA on Mountain Lion, rather than Mountain Lion being on the external SSD.

 

[jerryk]

The reason for this strategy is that I have important legacy software that can only run on Mountain Lion, so I wanted to keep the ML OS on the main drives of both the MBP and MBA, and then use the external SSD to run the latest macOS Sierra and later High Sierra.

I use the legacy software often enough such that I wish to keep the MBP and MBA on Mountain Lion, rather than Mountain Lion being on the external SSD.

Why not move the machines up to the latest versions of MacOS and run ML in a VM on each machine.

I am pretty sure Parallels supports MacOS on MacOS. Other VM managers may also provided this support.

 

[killawat]

Why not move the machines up to the latest versions of MacOS and run ML in a VM on each machine.

This is the probably the best approach. Push come to shove you could actually unlock a Windows VMWare Hypervisor (like VMware Workstation) so that you could run your Mac VMs.

Anywho, MacOS will support this fine, just like back in the days of FireWire target disk mode (which would be thunderbolt now). As long as the OS has drivers from both hardware revisions.

 

[minvoyager]

Why not move the machines up to the latest versions of MacOS and run ML in a VM on each machine.

For this thread, I am after advice on running Sierra off an external SSD, using to boot two Macs.

I realise people will suggest alternatives to that, such as running Mountain Lion off the external SSD instead.

The reason I don't want to do that, is that the legacy software is, itself, inside a VMWare, and I don't have the source files to restore both the MS Windows and legacy PC-software, if I had to re-install the legacy software from scratch.

 

[Benjinator]

I have done this and it is possible to run Mac OS off a USB external drive and use it on multiple Macs as long as the OS is supported.

 

[minvoyager]

I have done this and it is possible to run Mac OS off a USB external drive and use it on multiple Macs as long as the OS is supported.

Now that you've confirmed it can be done, can you comment on what degree of performance slowness it would have coming through a USB 3 external connection, compared to running the same SSD internally?