Apple’s documentation implies that you should not use Time Machine to backup photo libraries on that are located on external dirves.
“WARNING: If a Photos library is located on an external drive, don’t use Time Machine to store a backup on that external drive. The permissions for your Photos library may conflict with those for the Time Machine backup.”
I have been using Time Machine to backup an external drive, with photo libraries, and I have not receive any warnings or error messages.
Question: Will I be be able to recover or restore these photo libraries?
I want to make sure my photo libraries are safely backed up.
I think you are reading it wrong. The text says "don’t use Time Machine to store a backup ON THAT external drive."
Yes, this is true. Don't use an external drive for BOTH Time Machine and storing a Photos library. In fact, don't use an external dive for Time Machine any ANYTHING ELSE at all. Dedicate the entire drive to Time Machine. Don't store other files on it, don't partition it either.
Besides any permissions errors that could happen, a few other problems would arise. One is that Time Machine won't be able to judge the amount of space on the drive correctly if you are also putting other files there. This has led to Time Machine errors in the past. Second, Time Machine stores versions of files going back in time. Less space means it will fill up faster and be unable to store as many versions. Third, and most importantly, anything on the drive itself can't be backed up. Even if it could, like if you partitioned the drive to two volumes, you'd have one point of failure for those files. That drive breaks or is damaged and you lose the originals and the backup at the same time.
That aside, I think the situation you have is your Photos library is on a DIFFERENT external drive than your Time Machine backup. Is that right? If so, you are fine. That's not what the warning is about. It is about using the SAME drive.
I have a drive i use for photos plugged into my computer and also the Time Machine drive plugged in at the same time.
If i back up Time Machine, will it also back up the photo drive?
Arnie: Unless you exclude it in your Time Machine settings, it should, yes. Easy enough to check by just going to the external drive and entering Time Machine mode to see the history.