Time Machine can't complete backup, not thinning backups on My Cloud EX2 Ultra

I have a My Cloud EX2 Ultra, 2 TB. The Time Machine share has a maximum size of 1.9 TB. Its current size is 1.8 TB.

I have two MacBooks using the share for backup. Both are having the same problem, even when one has automatic backup turned off so that only one machine backs up at a time.

The problem: The backup gets to between 8 and 11 GB of the total amount to be backed up, then progress stops.

When this happens, here’s what else is going on:

  • macOS System Preferences > Time Machine says, “Freeing up space.”
  • Putting the computer to sleep stops the backup even though Power Nap is enabled.
  • After the backup is canceled (by clicking the {x} or by putting the computer to sleep), this error message appears in System Preferences:

  • The computer and the My Cloud EX2 Ultra are on the same network. The router confirms this. The error appears even when both devices are connected to the router by ethernet cable.
  • The My Cloud GUI reports its RAM hovering around 50% and its CPU usage at 0% with momentary spikes to 5–15%.
  • A check of the Mac’s log shows an extremely slow rate of backup thinning. For example, in one four-hour period, only 150 MB of space was cleared.

Log entries after backup is canceled:

Here’s what I’m looking for:

  1. If there’s a way to complete the backup in a reasonable amount of time with the current Time Machine history, tell me.
  2. If the only remedy is to delete the sparsebundle on the My Cloud and start over, can I expect this to happen again when total backup size hits 95% of share size?

Hi,

Please refer to the following KB article: Error: 'Time Machine could not complete the backup.' occurs when backing up to the Time Machine share

Hello, Neha_07. I see you’re advising me to delete the sparsebundle on the My Cloud and start over. To repeat what I wrote above, can I expect to run into the same problem when total backup size hits 95% of share size next time?