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I am attempting to migrate my Lightroom Classic library to Lightroom CC. I am getting the error about insufficient disk space. I have tried changing my storage location to a 2TB drive, but the migration tool still appears to be looking for space on my internal drive even after making the change. Also, the error says I need 66GB free, but macOS reports I have 70GB available. So I'm at an impasse.
I have researched a fair bit on the Adobe support articles and forums and have not found a solution. This thread linked below offers an "answer" but the steps provided do not resolve my issue.
Can a migration be performed using an external HD?
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It appears that Lightroom CC does not take the purgeable space into account that Mac OS X tells you is available. This is quite a problem as it prevents it from doing it's job even though there really is enough space available. Read more about purgeable space here: Rocket Yard Guide: What Is Purgeable Space in macOS? | Other World Computing Blog.​ and here: When free space isn't free: Purgeable storage in macOS Sierra - Six Colors
You can see how much of the free space is actually "purgeable" sp
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You can't use an external for migration. This seems to be a big weakness in Adobe's design of this process. You can store local copies on an external but for the migration it still needs all this internal disk space. This leaves people with small internal SSD drives in the cold indeed. The only solution I have seen is to migrate the catalog in smaller pieces. Basically you export ew catalog files from Lightroom classic into several smaller catalogs taking care to in the end have everything and to migrate those one by one, overtime waiting until everything is uploaded before you do the next one.
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Thanks Jao. I have since freed up the SSD so that there's over 90GB available according to macOS. However, I am still getting the same error, saying it needs 66 GB. How does Lightroom evaluate the disk's free space?
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Update: I have since learned about macOS Sierra and its deceiving reporting of free space. macOS says my drive has 132 GB free, but 80 GB of it is "purgeable." There is apparently no way to force the system to purge, so my actual free disk space is 53 GB. Not enough to do the migration.
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It appears that Lightroom CC does not take the purgeable space into account that Mac OS X tells you is available. This is quite a problem as it prevents it from doing it's job even though there really is enough space available. Read more about purgeable space here: Rocket Yard Guide: What Is Purgeable Space in macOS? | Other World Computing Blog.​ and here: When free space isn't free: Purgeable storage in macOS Sierra - Six Colors
You can see how much of the free space is actually "purgeable" space that isn't really free if you do a get info on your hard drive.
I do not know how to solve this issue easily unfortunately.
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This is probably due to APFS keeping "purgeable storage" around, and a bug in LR where it fails to access this perfectly usable space.
To hack around this, you can go into Terminal and do the following.
- $ df -h #shows 32G free
- Filesystem Size Used Avail Capacity iused ifree %iused Mounted on
- /dev/disk1s1 932Gi 896Gi 32Gi 97% 812940 9223372036853962867 0% /
- # this step takes a while -- monitor your disk space
- $ dd if=/dev/zero of=zeros bs=9000 #and then hit CTRL-C once your disk is completely full
- ^C17539950+0 records in
- 17539949+0 records out
- 350798980000 bytes transferred in 554.492292 secs (632648974 bytes/sec)
- $ rm zeros #delete the large temp file
- $ df -h #shows 328G free
- Filesystem Size Used Avail Capacity iused ifree %iused Mounted on
- /dev/disk1s1 932Gi 600Gi 328Gi 65% 812842 9223372036853962965 0% /
Then retry your import. This worked for me.

