Backstory:
I have a Windows 10 x64 Home PC I use as a backup NAS. The backup volume is a (12 + 10 + 0.12 + 0.25)TB DrivePool (read: 4 HDDs with the listed capacities.) The 12 TB HDD is on 3 Gb/s SATA connection, the 10 TB on a 1.5 Gb/s SATA connection, and the other 2 HDDs are are on a USB 3.1 Gen 1 connection. All of the drives are mostly empty, and I think they're all set to compress files to save space in Windows (the 2nd link below implies this may be an issue, but I'm not sure just yet.)
The last 3 (10, 0.12, 0.25 TB) drives are new additions to the DrivePool, which mostly empty. I rebalanced it recently. Last night a Veeam backup to the DrivePool from another PC on the LAN failed with an error message, containing: “The requested operation could not be completed due to a file system limitation.”
Some Googling of the error message brings up this Technet thread and this NTFS documentation page, which seem to imply that if files get too fragmented NTFS can no longer handle them.
Has anyone seen anything like this before? Any ideas?
Update: fixed via disabling compression on all drives, deleting contents of backup target folder, running balancing, and then trying the backup again.