make room on external hard drive time machine

Once you know you have a good backup, you can decide if it’s worth finessing the old backup or just let it be the history before Catalina and a place for manual backups of things like installers you download, second copies of photos and videos or just leave it on the shelf.

Leave both connected and the system will back up even/odd to each destination in turn. Next, I would just add a new drive - get whatever is less than $95 from a local store and set it up as a second destination. If that gets you past the conservitave estimate, you’re set. Open Time Machine preferences, select options and tick the box labeled Exclude system files and applications as shown below.

You shouldn’t have to do this by my math either, but it’s low hanging fruit to try. Since the read only system is split, you will have a larger than normal new backup interval. The first thing to try on Catalina is to tell it not to backup the system files and apps. Is it a genuine issue (it actually needs more than 500GB), or an error? How do I fix it without losing the old backups? I know that backups following a major macOS update take more space, but it should still fit comfortably in 505GB, and even if it didn't it should automatically clean old backups. That should be plenty to perform a new incremental backup of the MBA. The Time Machine drive is a 1TB hard drive with 505GB available. Now the upgrade to Catalina has completed successfully, but they can't backup to Time Machine anymore because 'there isn't enough space'. (I know, I know: they should have backed up right before upgrading, but now it's too late for that) The Time Machine drive is an external hard drive connected via thunderbolt (v1) cable and thunderbolt to USB-C adapter. They've been backing up the MBA with Time Machine more or less regularly, with the last backup completed 7 days before the upgrade. The MBA has got a 250GB SSD drive, of which only 80GB are in use (170 available). A family member has updated their MacBook Air from the latest version of Mojave to Catalina 10.15.1.

Make room on external hard drive time machine