How do I simulate normal hard drive performance on my SSD based Mac?

Question

What I Want

I want to simulate the performance of a normal hard drive on my SSD based development machine.

Background

I'm developing a Mac application on a Macbook with an SSD. It's gloriously fast.

If someone has a standard platter hard drive, my app will be slower for them. My app is heavy on Core Data too, so the disk access speed will be a significant factor.

I worry that the performance measurements I take with Instruments look fine, but when a customer runs my app on their normal hard drive it will be achingly slow.

What I've Tried

Before I installed my SSD, I measured the performance of my app in Instruments. After the install, I measured it again and the two benchmarks were identical.

This doesn't make sense to me. I'm convinced I was doing something wrong here. Instruments probably measures clock speed, not wall time speed. But still, surely the speed of the hard drive should affect the benchmark I took? Or does Instruments somehow compensate for this?

Answer 1

Kudos to @PaulR above who suggested using an external USB hard drive to test performance. Thanks!

Answer 2

You can use a Virtual Machine and throttle disk access. In this way you should have control over disk speed.... still not possible to limit only writes or only reads.

Here are some tips about how do it in Virtualbox 5.8. Limiting bandwidth for disk images https://www.virtualbox.org/manual/ch05.html#storage-bandwidth-limit