Two System Photos Libraries on one external drive

[hewhore]

I just bought a 2TB SSD to move both mine and my partner's Photos libraries to. I will choose the 'Download Originals' option within both libraries, as I eventually want to stop using iCloud to store our photos and move to either Carbon Copy Cloner or Time Machine to back up the originals. Each library is approximately 500GB. My question is about formatting the SSD: As there will need to be two System Photos libraries on one drive, (one for me, one for my partner), should I create two APFS volumes within the SSD's container? Or two partitions?

 

[gilby101]

Please confirm that you each have your own macOS username and your own iCloud/Apple ID.

 

[hewhore]

Yes to both.

 

[Mike Boreham]

….should I create two APFS volumes within the SSD's container? Or two partitions?

I don't believe it matters. Since both are APFS I would have them in same Container so that they are space sharing. The only use case I have found where separate partitions are essential is when you need to have different file systems, eg HFS for bootable installers. OTOH I have not tried what you are doing, so it might be another.

 

[hewhore]

Thanks @Mike Boreham, I created two volumes in the same container.

 

[gilby101]

I created two volumes in the same container.

Keeps them clearly separate, even if not necessary.

More important, I suspect, is having two usernames. Even without the Photos app running, I have 7 background processes running which have most (all?) my Photos libraries open. So it may be critical not to have any shared Photos libraries - but if you have one each that is easy.

I have just done a test with a second user. I have both logged in (with fast user switching) and each with a separate Photos library open. No obvious issues. So your plan looks good.

 

[HDFan]

should I create two APFS volumes within the SSD's container?

No. If one volume runs out of space you are out of luck. With both in one container you can use all available space on the drive.

 

[Mike Boreham]

No. If one volume runs out of space you are out of luck. With both in one container you can use all available space on the drive.

That looks like a typo? Did you mean 'yes'? As you say, two APFS volumes in the same container will share the space.

 

[FreakinEurekan]

I do exactly this with my own Mac, and I’m using a single APFS volume. The user accounts keep the files straight.

 

[hewhore]

That looks like a typo? Did you mean 'yes'? As you say, two APFS volumes in the same container will share the space.

That was my understanding with how volumes on an APFS formatted drive work: One will automatically make space for the other if the other requires it, hence the 'quota' and 'limit' options in Disk Utility when formatting a drive.

 

[Mike Boreham]

That was my understanding with how volumes on an APFS formatted drive work: One will automatically make space for the other if the other requires it, hence the 'quota' and 'limit' options in Disk Utility when formatting a drive.

That's my understanding too. So wondered why you said "no", responding to the question "should I create two APFS volumes within the SSD's container?" APFS space sharing is great! Saves having to predict what size to chose for separate fixed size containers.

Sorry ...crossed out bit was when I thought I was replying to HDFan again!

 

[HDFan]

One will automatically make space for the other if the other requires it,

Oops, was thinking of partitions rather than volumes as you said. Stand corrected. However see no point in setting up 2 volumes. Makes backups more complicated.