Avago Technologies 3ware SAS 9750-4i - Manual (Page 25)

Understanding RAID Levels and Concepts
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Through drive coercion, the capacity used for each drive is rounded down so
that drives from differing manufacturers are more likely to be able to be used
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 will be rounded down to 44 GB, and a 123 GB drive will be rounded
down to 120 GB.
Support for Over 2 Terabytes
Legacy operating systems such as Windows 2000, Windows XP (32-bit),
Windows 2003 (32-bit and 64-bit without SP1), and Linux 2.4, do not
recognize unit capacity in excess of 2 TB.
If the combined capacity of the drives to be connected to a unit exceeds 2
Terabytes (TB), you can enable auto-carving when you configure your units.
Auto-carving divides the available unit capacity into multiple chunks of 2 TB
or smaller that can be addressed by the operating systems as separate
volumes. The carve size is adjustable from 1024 GB to 2048 GB (default)
prior to unit creation.
If a unit over 2 TB was created prior to enabling the auto-carve option, its
capacity visible to the operating system will still be 2 TB; no additional
capacity will be registered. To change this, the unit has to be recreated.
You may also want to refer to Knowledge Base article # 13431, at
https://selfservice.lsi.com/service/main.jsp . (Use Advanced search and enter
the KB # as a keyword.)
Note: All drives in a unit must be of the same type, either SAS or SATA.