Disk Summary – Systems Engineering & Integration

Directly-attached storage is commonly implemented in the following ways:

Internal hard disks using an internal bus and IDE, SCSI, or SATA drives
External USB, eSATA, or FireWire disks
Rack mounted storage connected to the server through an external connector or external bus

When you add a new disk to a Windows Server 2012 system, you will be prompted to initialize the disk and select a partition style. The partition style identifies how information about disk partitions are stored. The following table identifies the two partition styles of disks:

Master Boot Record (MBR)

Master Boot Record (MBR) is the traditional partitioning method. MBR provides:

Backwards compatibility with Windows operating systems.
Support for up to 4 partitions.
A maximum partition size of 2 TB.

With MBR, partitioning information is often stored in hidden locations on the disk or even within the operating system. These locations might vary from vendor to vendor.

If you do not have a disk larger than 2 TB, use MBR.

GUID Partition Table (GPT)

GUID Partition Table (GPT) is a disk partitioning method introduced with Windows Server 2008. GPT provides:

Support for up to 128 partitions (Windows restriction).
Support for partitions larger than 2 TB.
Partitioning in Windows Server 2008, Windows Server 2008 R2, and Windows Server 2012.

With GPT, partition information is stored on the disk in well-documented locations. Each partition is identified by a GUID number. GPT also provides redundancy for the partition table.

You can convert between MBR and GPT as long as there are no volumes on the disk.

A volume identifies an area of disk space that the operating system can use for storing data. A volume is either basic or dynamic, depending on the type of disk on which the volume resides.

Basic

A basic disk supports volumes made up of contiguous disk space. Basic disks have limitations depending on the partition style used:

On an MBR disk, a basic disk has a limit of four partitions.
- You can have up to four primary partitions or up to three primary partitions and one extended partition.
- The extended partition can be divided into multiple logical drives.
On a GPT disk, Windows imposes a limit of 128 partitions. GPT disks do not have an extended partition.

On basic disks, you can shrink or extend volumes only on the same disk. Basic volumes correspond to the primary or extended partitions on the disk.

Dynamic

A dynamic disk supports volumes from contiguous and non-contiguous disk space.

Dynamic disks support up to 128 volumes on both MBR and GPT disks.
Dynamic volumes allow you to extend existing volumes to include non-contiguous space on the same disk, to extend a volume onto a different disk (creating a spanned volume), or to implement striping or mirroring.
Each dynamic disk stores a replica of the dynamic disk database for all dynamic disks connected to the system.
The dynamic disk database facilitates volume management.
On a new server, import dynamic disks as a unit. The disks will be marked as foreign.

The main reason to choose dynamic over basic disks is to take advantage of advanced disk configurations that involve spanned, striped, and mirrored volumes. It is best practice to convert a disk to dynamic only when the volumes require more than one disk.