Avago Technologies 3ware SAS 9750-16i4e - Manual (Page 26)

Chapter 1. Introduction to the 3ware Command Line Interface
18 3ware SATA+SAS RAID Controller Card CLI Guide, Version 10.2
Through drive coercion, the capacity used for each drive is rounded down to
improve the likelihood that you can use drives from differing manufactures as
spares for each other. The capacity used for each drive is rounded down to the
nearest GB for drives under 45 GB (45,000,000,000 bytes), and rounded
down to the nearest 5 GB for drives over 45 GB. For example, a 44.3-GB
drive is rounded down to 44 GB, and a 123-GB drive is rounded down to
120 GB.
Note: All drives in a unit must be of the same type, either SAS or SATA.