The adapter is used for transferring the operating system from the MBPro to the new drive before it's installed.
I hadn't read about SSD's getting slow. I guess it would do me good to spend more time researching them before I make the mistake of buying one. Thanks for the heads up!
OWC has complete instructions on transferring information from the computer to the new drive using the adapter. They also have instructions on how to disassemble the computer and change out the drives.
SSDs do get slow as they age. They start out about 60x faster than any mechanical hard drive, but by the time you've been using them for five or six years, they slow down so they are only about 57x faster than any mechanical hard drive.
SSDs have a limited life. A modern third-generation SSD that you buy today can have each cell written to about 2 million times before it wears out. Cheaper second-generation SSDs have half that life; you can write to one block about a million times before it wears out. The drives use all sorts of tricks to extend their lifespan; "wear leveling" means that they shuffle data around so that all the blocks have the same amount of wear, and "overprovisioning" means that they have millions of spare transistors so that when one wears out, they start using a spare.
In practical terms, that means if you write huge amounts of data--say, three terabytes of data per day, 24 hours a day, 7 days a week--an older drive will last about fifteen years, and a newer drive will last about 30 years. That's not accounting for wear leveling or overprovisioning. Since drives use both of those to manage life, if you're writing three terabytes of data per day, 24/7, an older drive will actually last closer to 20 years, and a newer drive, 40 years.
If you don't do that kind of incredible volume of writing, but your usage is more typical of home users (watching streaming movies, doing word processing and email, surfing the Web), a cheap drive will probably last you 40-50 years, and a more expensive drive will likely last 70-90 years.
When people talk about an SSD having a limited lifespan, they forget that normal hard drives also have a limited lifespan, too. The lifespan of a normal drive depends mostly on how long the bearings will last. The platters spin at thousands of RPM, and even modern sealed bearings still wear out. The difference is that an SSD only wears when you write data; there is no wear from reading information off the drive. A normal hard drive, on the other hand, is wearing out the entire time it is spinning, even if the computer's not using it.
