Can I share external drives between Macs with different Mac OS?

[Soppakey]

I have two Macs, one stuck using High Sierra (unable to upgrade to any newer OS) and one using Monterey.
I have tried to access external drives that are connected to the Monterey Mac, using the HS Mac, and which has been successful sometimes.
However, other times I cannot access the external drives in this way. I can't work out what I need to do to make access consistent and I haven't found any help on the topic when I have searched (Apple's user support forum is now abysmal/tumbleweed town hence my coming here).

I have also found inconsistent access to the Monterey Mac from the HS Mac when using apps and I haven't been able to understand why. Access to the HS Mac from the Monterey Mac has been fine all the time.
I often have to either reboot both Macs, or restart the finder on both Macs, or doing both, which sometimes works but not every time.
Booting the HS Mac is a real chore now, as it takes around 5-10 mins to restart, software to load, etc., and for the hard disk to stop thrashing about and ready for use.
This access is when I want to transfer files and folders as well as other uses with apps.

 

[usagora]

Sounds like it's time to start a replacement plan for the HS Mac.

So, are you saying sometimes the external HD connected to your Monterey Mac will show up in Locations (e.g. on Finder sidebar or on your Desktop) on your HS Mac, but then just disappear without anything else happening in between (e.g. putting one or both of the Macs to sleep, rebooting, etc.)?

 

[Soppakey]

So, are you saying sometimes the external HD connected to your Monterey Mac will show up in Locations (e.g. on Finder sidebar or on your Desktop) on your HS Mac, but then just disappear without anything else happening in between (e.g. putting one or both of the Macs to sleep, rebooting, etc.)?

No (partly). There is no Locations section of the finder left sidebar on the HS Mac. I can only access the external drive connected to the Monterey Mac, by accessing the Monterey Mac which shows up in the Shared section of the Finder's left sidebar and then I can select the external drives, all of which have folder icons before their name (with some kind of graphic inside the folder). But yes, sometimes, either the Monterey Mac will disappear from the Shared section on the left sidebar, or the external drives do not appear if the Monterey Mac shows on the left sidebar and I select it. Occasionally, the external drives do appear after a long time (hours).

 

[Fishrrman]

For ALL my external drives (USB flash drives, hard drives, SSDs, etc.) I use HFS+ and NOT APFS.

This way the drives remain compatible with older OS's.

The ONLY drives that are APFS are those that MUST BE in APFS -- such as boot drives for newer versions of the OS that require APFS.

 

[Soppakey]

I'll keep that in mind but it doesn't help now.

 

[Brian33]

But yes, sometimes, either the Monterey Mac will disappear from the Shared section on the left sidebar, or the external drives do not appear if the Monterey Mac shows on the left sidebar and I select it. Occasionally, the external drives do appear after a long time (hours).

I don’t guarantee this will work, but it’s probably worth a try as a workaround: when the Monterey Mac is missing, go to the Monterey mac’s SystemPreferences>Sharing and DISable (uncheck) file sharing. Wait a few moments and then re-enable it. Now check your High Sierra Mac to see if Finder now shows the Monterey Mac.

I have a somewhat similar problem, and this procedure always lets the HS Mac “see” the Monterey mac’s shared drives.

 

[Soppakey]

I don’t guarantee this will work, but it’s probably worth a try as a workaround: when the Monterey Mac is missing, go to the Monterey mac’s SystemPreferences>Sharing and DISable (uncheck) file sharing. Wait a few moments and then re-enable it. Now check your High Sierra Mac to see if Finder now shows the Monterey Mac.

I learned of this workaround through Apple support a few years ago when neither Mac could see the other (The Apple support person couldn't solve the problem, after over 1.5 hours on the phone with them.
I have not changed anything since (except the OS updates) but now both Macs can see each other all the time.
The only exception arises from the HS Mac not showing the Monterey Mac in the shared section sometimes, but this is rare now.

Its the intermittent nature of this problem that puzzles me the most, because in computing its either yes or no. Maybe isn't a real option. But as someone told me many years ago, the strangest things you will find in life are in electronics.

 

[jel888]

I don’t guarantee this will work, but it’s probably worth a try as a workaround: when the Monterey Mac is missing, go to the Monterey mac’s SystemPreferences>Sharing and DISable (uncheck) file sharing. Wait a few moments and then re-enable it. Now check your High Sierra Mac to see if Finder now shows the Monterey Mac.

I have a somewhat similar problem, and this procedure always lets the HS Mac “see” the Monterey mac’s shared drives.

This is more of a request for a detailed reply to the original question (for a newbie to sharing on Apple devices). Your answer seems to give me part of it. I'd like to know how do you set it up from scratch? If in my case I'll have an SSD that I want to use to Time Machine save and data store to one external SSD (I may partition it if recommended) for multiple Apple devices (one iMac M1, one iMac Intel and one MacBook Air on BS). Will I need hard (cord) connections or can simply share the drive you describe here?

 

[Brian33]

If in my case I'll have an SSD that I want to use to Time Machine save and data store to one external SSD (I may partition it if recommended) for multiple Apple devices (one iMac M1, one iMac Intel and one MacBook Air on BS).

Here's what I would do: connect the external SSD to one of the Macs (I'll call it Mac 1). The drive is directly-attached to Mac 1, so Time Machine's backups are slightly different... by default Mac 1 will want to use the entire disk for backups (I'm pretty sure). To prevent that, you can create a partition on the SSD for Mac 1's backups.

For Mac 2 and Mac 3, you could create two more partitions for a total of three, but you don't have to -- an alternative would be to create separate folders for Mac 2 and Mac 3 backups in the single remaining partition.

I think using folders is slightly more flexible, because you can change the backup limit size later (see Step 9 below). If you go with using folders, format the remaining partition as APFS and create, for example, Folder 2 and Folder 3.

Now you want to share Folder 2 and Folder 3 over the network to the other Macs. Follow directions in this Apple document:
https://support.apple.com/en-au/guide/mac-help/mchl31533145/12.0/mac/12.0

Note Step 9, where you can limit how big the backup space can grow for Mac 2 and for Mac 3, and the limits don't have to be the same. Even if you don't set limits, the two backup "sparsebundle" files (one for Mac 2 and one for Mac 3) should be able to live compatibly, using all space eventually. But you will have less control over which machine gets more backup space (which translates to which machine has a longer backup history available).

Now go to Mac 2's Time Machine preferences, and the new shared folders should appear as possible backup destinations for Time Machine. Same for Mac 3.

Ideally, at least Mac 1 (the "file server") will be connected to your network with an Ethernet cable instead of WiFi, but it all should work over WiFi if necessary.

Hope that helps!

 

[jel888]

Here's what I would do: connect the external SSD to one of the Macs (I'll call it Mac 1). The drive is directly-attached to Mac 1, so Time Machine's backups are slightly different... by default Mac 1 will want to use the entire disk for backups (I'm pretty sure). To prevent that, you can create a partition on the SSD for Mac 1's backups.

For Mac 2 and Mac 3, you could create two more partitions for a total of three, but you don't have to -- an alternative would be to create separate folders for Mac 2 and Mac 3 backups in the single remaining partition.

I think using folders is slightly more flexible, because you can change the backup limit size later (see Step 9 below). If you go with using folders, format the remaining partition as APFS and create, for example, Folder 2 and Folder 3.

Now you want to share Folder 2 and Folder 3 over the network to the other Macs. Follow directions in this Apple document:
https://support.apple.com/en-au/guide/mac-help/mchl31533145/12.0/mac/12.0

Note Step 9, where you can limit how big the backup space can grow for Mac 2 and for Mac 3, and the limits don't have to be the same. Even if you don't set limits, the two backup "sparsebundle" files (one for Mac 2 and one for Mac 3) should be able to live compatibly, using all space eventually. But you will have less control over which machine gets more backup space (which translates to which machine has a longer backup history available).

Now go to Mac 2's Time Machine preferences, and the new shared folders should appear as possible backup destinations for Time Machine. Same for Mac 3.

Ideally, at least Mac 1 (the "file server") will be connected to your network with an Ethernet cable instead of WiFi, but it all should work over WiFi if necessary.

Hope that helps!

Thank you so very much! I wanted to see if this was viable versus putting in a NAS. I can't afford this right a NAS (with SSD) right now and want to avoid opening up a security risk (this is for a small business @ home) while still needing to ensure data backup. I see that you didn't mention a hard (cable) connection between the Apple devices (as I've seen mentioned in another article), only the ethernet of the main Mac 1 to my router. Is this for better data transfer or security (or both)? Again, thanks so much! God bless you and much appreciated!

 

[Brian33]

I see that you didn't mention a hard (cable) connection between the Apple devices (as I've seen mentioned in another article), only the ethernet of the main Mac 1 to my router. Is this for better data transfer or security (or both)?

In my opinion, connecting your devices (Macs) to your network with Ethernet cables is preferred only because it is usually faster data transfer (although that depends upon your WiFi setup), and it can be more reliable (again, depends upon your specific environment). However, if you have a good reliable WiFi network set up and all devices have a good connection, hard-wired connections are not needed. A lot depends upon how many competing WiFi networks are in the same area, the specific WiFi hardware, and how far from the WiFi access point the device is.

As far as I know, there shouldn't be a big difference in security if you are using a modern WiFi router or access point (with at least WPA2 security. WEP is an older unsecure protocol but I doubt you are using that).

If you don't use wired connections right now and everything seems to work OK, I'd go ahead and try the Time Machine remote backups with your current setup and see how it goes!

EDIT: one thing to keep in mind is that the very first backup of a Mac over a network might take a long time -- like overnight or a whole day! That's OK -- subsequent backups will probably be unnoticable.

 

[jel888]

In my opinion, connecting your devices (Macs) to your network with Ethernet cables is preferred only because it is usually faster data transfer (although that depends upon your WiFi setup), and it can be more reliable (again, depends upon your specific environment). However, if you have a good reliable WiFi network set up and all devices have a good connection, hard-wired connections are not needed. A lot depends upon how many competing WiFi networks are in the same area, the specific WiFi hardware, and how far from the WiFi access point the device is.

As far as I know, there shouldn't be a big difference in security if you are using a modern WiFi router or access point (with at least WPA2 security. WEP is an older unsecure protocol but I doubt you are using that).

If you don't use wired connections right now and everything seems to work OK, I'd go ahead and try the Time Machine remote backups with your current setup and see how it goes!

Thank you again! Okay, so now I'm staring at a 5-port gigabit desktop switch I purchased on a whim and now thinking from what you've said that I should connect it to the two iMacs (which will handle most of the business) and the Macbook could remain on the Wifi. Definitely on WPA2. That's how I'll start, and as you said, "see how it goes!"

 

[Soppakey]

Yesterday, my HS Mac lost the connection to the Monterey Mac. A message appeared on my screen.
The Monterey Mac still shows on the Finder sidebar Shared section but when I click on it, it is slow to show the volume name (about 15 seconds) and then clicking on a folder also take a long time (minutes). I tried to transfer some files to the Monterey Mac after this loss and got a failure message (about some of the files being in use, which they were not).
I am trying again now and will see if it works this time (it has done in the past if I wait some time). If not, I will have to reboot both Macs, which seems to do the trick.

Getting a new/newer Mac will probably solve this issue for me but its not an option right now.

 

[Soppakey]

I don’t guarantee this will work, but it’s probably worth a try as a workaround: when the Monterey Mac is missing, go to the Monterey mac’s SystemPreferences>Sharing and DISable (uncheck) file sharing. Wait a few moments and then re-enable it. Now check your High Sierra Mac to see if Finder now shows the Monterey Mac.

I have a somewhat similar problem, and this procedure always lets the HS Mac “see” the Monterey mac’s shared drives.

This tip worked for me just now, after rebooting.