Optimizing Spotlight for Better Performance
Spotlight can interrupt important work, suck up CPU time, and generally make a nuisance of itself at inconvenient times. The benefits of Spotlight are truly useful, yet it is possible to benefit from it and yet be less annoyed with its interruptions*.
The Spotlight process is the obtusely-named “mds” as seen in Activity Monitor.
* Over the years, Apple has taken no action to make Spotlight behavior predictable or controllable. It is a constant nuisance for your author when erasing and testing drives (repetitive exclusion), when backing up, etc.
Backup 4X too slow?
Spotlight might decide to start indexing the backup (or original) volume while the backup is in progress, causing a huge slowdown in backup speed (doubling or even quadrupling the required time, not to mention sucking up CPU time).
I never want the backup volume indexed by Spotlight — it’s pointless for me.
The solution? Exclude all backup volumes, and remember that after erasing a volume, you’ll have to re-exclude it; Spotlight forgets excluded volumes once it’s erased, even if the name remains the same.