Time Machine backup slows after Tahoe upgrade
Time Machine stopped working for me a few weeks ago.
I have three external hard drives that I use for backup and I rotate the three. After upgrading to Tahoe a few weeks ago, I successfully backed up to the first drive in my rotation. However, when I went to backup to the second, it got stuck for a very long time. It did not get stuck in the "preparing backup" phase. Instead, after copying a few gigs relatively quickly, it slowed to a crawl...we're talking a few megabytes per hour. I know that sometimes Time Machine has to delete old backups, so I let it sit...for six nights! Six nights later, it was still crawling at a few MB an hour, not having even progressed a gig in six days. I've had Time Machine get stuck for hours cleaning out old backups, but never days.
Maybe something's wrong with my second backup drive, I thought, so I'll try the third in my rotation. Same problem, so the problem wasn't the drive.
Then I decided to try a fresh backup. I reformatted a 2TB hard drive (to back up about 400GB from a 512GB machine). Same problem. Time Machine copied the first 250GB or so quickly, then slowed to a crawl. Obviously, the problem isn't that Time Machine is clearing up space on the backup drive because this was a large and empty drive.
I've tried other things...
--I restated my Mac. No difference.
--I read somewhere that you need space on the drive being backed up, not just the target drive, so I hand copied about 50GB of data off my Mac's hard drive. Even with the extra empty space on the source, the problem did not go away.
--Given that the fresh backup got through 250 GB before slowing down, I thought that maybe Time Machine is having trouble accessing something on my hard drive, so I ran Disk Utility to see if it found any problems. Other than a few minor things, it found none, and the problem continued afterwards.
I do not have any antivirus software installed. I have not changed anything on my Mac recently other than installing Tahoe, and even that isn't necessarily the culprit because, as mentioned above, I backed up once successfully after upgrading.
Any suggestions? I'm very frustrated. Thanks.
