[vidarh]

In nearly every large system I've been involved in designing, a "filesystem is a filesystem" would give you a great chance of rendering the system non-functional or performing so bad it might as well be non-functional when making simple design decisions based on knowledge about the problem made it easy to avoid in the first place.

Premature optimization is a sin, but making design decisions you know from experience has a major impact is not, as long as you measure to confirm afterwards.

We don't design by throwing dice - most decisions we make are based on experience or assumptions about what works and what doesn't. Measurements are important to challenge those assumptions, but it doesn't take away the value of making use of experience to create a reasonable baseline.

Where "premature optimization" comes in is where you start expending unnecessary extra effort to implement a more complicated solution without evidence to back up the need for it.

Spending a little bit of time to think through the requirements for major aspects of your system is not extra effort.