All disks cache data to be written, which makes benchmarking them tricky. It has more serious consequences which macOS tries to allow for in file systems and backups.
backup
Why Time Machine makes snapshots, and how they can grow and apparently consume free space. What you can and should do to manage this.
Problems with the file system of Time Machine backups haven’t gone away with APFS. As there’s no way to copy your backup volume, how to tackle such problems?
Is it overhead from sandboxing, the file system, the throttling of I/O, or the limitations of the Efficiency cores? Is there anything a user can do?
Since Catalina, reports of Time Machine backups slowing to a crawl have become common, but the reasons are unclear. It’s time for Apple to inform us.
Have you got problems backing up to your NAS? Here is a series of four simple tests to perform to give clear insights and help you tune its performance.
Backing up using Time Machine over Gigabit Ethernet to another Mac providing shared backup storage in Monterey 12.1 delivered good performance of 35-43 MB/s.
Tired of HFS+? Disenchanted by APFS? Why not copy or back up to a different file system? Here are crocodiles waiting to bite you.
How to repair a snapshot with an error when it’s one of your backups on a hard disk? Currently this seems impossible, putting all those backups at risk.
Don’t waste time trying to discover which files are still open when you want to check or repair an APFS disk and Disk Utility throws an error. Here’s the solution.
The Eclectic Light Company 