Are there any disadvantages to unusual RAM amounts for virtual machines?

Solution 1:

I've never ever seen any proof that the precise value of RAM matters on a virtual machine. I suppose it's not implausible that some legacy systems may somehow expect an even number, but that would just be incredibly bad engineering.

Certainly - it's pretty natural for people to allocate in multiples, but this tends to be because they know Server [A] needs 8GB of RAM, rather than 7GB.

If you want to give you server 3GB, then absolutely go right ahead; I use odd numbers all of the time.

Solution 2:

It's fine. There's no downside. Remember, the granularity is is Megabytes, so if you need 2,560MB instead of 2GB or 3GB, it's fine, fully supported and a non-issue.