

When it gets there due to filling, you will experience slow and lazy functioning, and errors. An ideal hard disk should never reach beyond 85% capacity, more specifically- a startup disk. Your startup disk keeps filling with utilization and when it is almost full, this problem arises. Most 0f the Mac users have just one disk but the power users may have two or more

In the language of Apple’s Support article, a Startup Disk is a volume or partition of a drive that contains a usable operating system. Mac hard drive consists of disks (or partitions) that has your Mac data on it, viz.- your operating system, applications, etc. Your Startup Disk is Full: All You Need to Know Update your MacOS to Use Optimize Storage

