SSD Life Time Measurements

I’ve been looking at possibly upgrading one of my Hyper-V servers to use SSDs. I don’t have the budget yet, but have been pricing up various options. One issue that arises is about the life time of the SSD, also referred to in the literature as endurance. There seems to be two separate measurements in use: Terabytes Written (TBW) an Drive Writes Per Day (DWPD). At first, I could not see the relationship – which kind of made comparing harder.

I did a little searching and found this neat article:  Comparing DWPD to TBW which provides a nice equation for converting DWPD into TBW. The trick here is to consider the warranthy period. DWPD is a measure of how many times you can totally overwrite the disk each day and not have it fail during it’s warranty period. To convert that to TBW, as the artilce points out – you multipy DWPD by warranty period (in days) and capacity (in TB).

I am starting to see more virtualisation projects using SSD disks, so the comparison betwen vendors and product lines is important. I wish there was just ONE measure of endurance, but such is life.