If you’ve bought a new Mac and/or a new SSD, do not assume that the drive + Mac is performing properly— test it, because some new MacBook Pro units have had defective logic boards. That principle applies to any new Mac.
Furthermore, there is dreck out there in the SSD market, so if you opt not to buy my recommended OWC solid state drives, at least test what you do buy.
I test my drives using the DiskTester fill-volume command, part of my software, diglloydTools. DiskTester fill-volume outputs data that can be pasted into a supplied Excel spreadsheet for an instant graph, and it’s good for hard drives or SSDs.
The Intel 510 SSD shows lousy write performance in my MacBook Pro, well below the speeds claimed by the specifications. Why pay a premium price for this low performance? Test, don’t assume.