The Unreliable Time Machine

Many bytes have been spilled the past few years over macOS’s declining software quality. This piece recounts an aspect of my own experience with this. I have been using Time Machine to backup and restore files since Apple introduced the feature back in 2007 with OS X Leopard. The space-age UI was both cool and convenient for retrieving files. But more importantly, the simplicity of hourly backups with intelligent rotation was a hassle-free experience. Time Machine has saved me numerous times over the years.

The story begins in August 2025. I had kept my iMac on macOS 13 because new macOS “major versions” in recent years come with no compelling new features and a significant chance of compatibility issues. But with Apple dropping security update support for macOS 13, I upgraded to macOS 15.

My backup drive was HFS+ formatted, but Apple had rewritten Time Machine to be optimized for APFS starting in macOS 11. Despite that, I experienced no backup issues when running macOS 13. After upgrading to macOS 15, I regularly encountered problems:

• Performance was abysmal; incremental backups sometimes took more than an hour. My backup drive is spinning-disk, but this had not been a problem before.
• Time Machine would accumulate tons of local snapshots on my boot device, eating into available disk space, without cleaning them up.
• Backups would periodically error out with no clear indication of what failed or why.

Then, one afternoon in November, I noticed that Time Machine was performing an exceptionally large backup. Somehow, Time Machine had convinced itself there was not enough space on the backup device, and it erased nearly two years worth of backup data to “make room”—despite the backup drive being double the capacity of the source volume. This was a significant loss, but thankfully I do have other backups that are not managed by Time Machine.

Given the situation, I took the opportunity to reformat the drive as APFS. Afterwards, the performance problems improved marginally, but the accumulation of local snapshots and periodic errors remained. Then in January, Time Machine went berserk and erased all of the backups on the disk to “make room” again. After reformatting, there was ample space for the incremental backups it was performing, so I cannot reason why Time Machine did this (nor could the logs answer the question). My faith in Time Machine had been completely eroded: a backup system that silently starts erasing all of your snapshots for no reason is unreliable.

After hearing about Arq Backup for several years, I trialed it in January, and now I’m a convert. Backups are faster than with Time Machine, snapshots don’t pile up, and the logs provide detail. The flexibility of configurable inclusions/exclusions and custom retention is also nice as a power-user. I opted for Arq Premium because the included cloud storage is competitively priced with object storage. I considered using Restic, which I use on all of my Linux hosts, but I value the tighter OS integration that Arq provides.

The only feature that Arq is missing is being able to browse snapshots at a given path over time, like the Time Machine interface. Arq only lets you navigate by individual snapshot, and you need to re-traverse the path if you want to consider a different point in time.