Not so much in my experience, but it’s somewhat faster. Most time on the import process is often spent to convert source assets into Unity’s proprietary format, rather than IO.
Think of converting a large texture to ETC format, it takes a long time to complete, especially if it’s using high-quality mode. Importing and compressing a long(er) audio file takes quite long as well. In both examples, a SSD would not help.
SSD probably helps when Unity is just loading small assets that don’t have a conversion step, but this is pretty fast anyway.
- In order to by-pass the compression step, you can use turn off “Compress Assets on Import”:
Unity - Manual: Preferences
The downside when turning off “Compress Assets on Import”, it that Unity will still compress them when building a Player. If you don’t do this (often), maybe it’s already an option for you.
- Another approach to speed up the import process is to use the Cache Server. They also support a “Local” mode, where you just run it on the same computer.
https://docs.unity3d.com/Manual/CacheServer.html
The Cache Server idea is that once an asset has been imported, Unity caches the result. The next time the asset is requested and it wasn’t modify in the meantime, it can be served from the cache.
If you work in a team in the same network, you normally want to use a Cache Server. Then just one person, the one who adds the asset, has to wait for the long import process. Other team member automatically get the cached files, which is just a file copy.
Another use-case when you want to use the Cache Server is if you often switch platforms. Like you need to build for iOS, Android, etc and always have to switch the build target.
Unity Technologies have mentioned at various Unite talks they’re either working or want to work on import pipeline performance improvements. They are aware of the problem, the improvements are just not available at the time of writing. Unfortunately, I wasn’t able to find that talk right now, just the general “performance by default” talk. It starts at around 17:10.
Unity at GDC - Evolving Unity