4. Configuring disk drives
As a Windows administrator, it is important
that you understand how to manage and configure disk drives. You can initially set up disk drives
and partitions during the installation of the OS; however, you may want
to add disk drives or provide more advanced disk functionality after
installation. We will now take a look at different disk configuration
and management features in Windows Server 2008 R2. After the OS is
installed, disk drives can be managed via the command prompt using the
diskpart utility or the GUI Disk Management MMC found in Server
Manager. You can access Disk Management by opening Server Manager, by expanding the Storage node, and by selecting the Disk Management node.
Basic disks versus dynamic disks
Windows Server 2008 R2 disk drives can be set
up as Basic Disks, the default, or Dynamic Disks which provide more
advanced features, such as the ability to create a RAID set for
increased performance and fault tolerance. If you want to perform
software-based RAID, opposed to hardware-based RAID, you will need to
change the disks that will be part of the RAID array to Dynamic. You
can convert a basic disk to dynamic by right clicking on the disk in
Disk Management and then choosing the option Convert to Dynamic Disk… as seen in Figure 3.
Notes from the field
Hardware RAID and disk drives
Most server hardware vendors recommend that
disk drives be set up as basic disks when using hardware-based RAID
configurations. Refer to your server hardware documentation prior to
changing disk drives to dynamic.
Dynamic disk volumes
Once disks are converted to dynamic, they can be configured to support the following types of volumes:
-
Simple Volume: A simple volume is the same as a single partition when using basic disks. A simple volume does not provide redundancy.
-
Spanned Volume: A spanned volume is one that can span multiple physical disk drives that logically appear to the OS as a single drive.
-
Striped Volume:
A striped volume provides software RAID level 0 functionality. RAID
level 0 does not provide redundancy in the event of disk failure but
does enhance the performance of multiple disks via striping data across
two or more disk drives.
Notes from the field
Disk striping
Disk striping is a technology that has been
around for years now. It allows data to be “striped” across multiple
disks to enhance disk performance. Instead of one disk read/write head
being used to write data, multiple heads from multiple disk drives can
be used to write data, thus increasing the performance. Typically, the
more disks added to the stripe set, the faster the performance.
-
Mirrored Volume—A
mirrored volume provides software RAID level 1 functionality. Two disk
drives are set up as a mirror set, and data that is written to the
primary drive is also written to the secondary drive. In the event that
the primary disk drive fails, the second disk drive contains the
“second copy” of the data and can become the new primary disk drive in
the RAID configuration. This technology ensures data fault tolerance
and redundancy, but you lose the performance enhancements gained by
disk striping.
-
RAID-5 Volume—A
RAID-5 volume provides software-based disk striping with fault
tolerance. A RAID-5 volume contains three or more physical disks to
create one logical disk drive as seen in Figure 4.
A RAID-5 volume gives you the performance benefits of a stripped set as
seen in striped volumes, while providing disk fault tolerance as seen
in mirrored volumes. In RAID-5 volumes, any single disk can fail in the
array without any loss of data.
Notes from the field
Disk hot spares
Some servers provide the ability to add a “hot
spare” disk drive. Hot spares provide additional redundancy by
providing a standby drive dedicated to replacing a failed drive in a
disk array. Traditionally, if a disk drive failed in a disk mirror or
RAID-5 array, the administrator would need to immediately replace the
failed drive, as failure of a second drive would result in loss of data
on the disk array. By using a hot spare, the server will automatically
add the standby “spare” drive to the mirror or RAID array and start
rebuilding that array.
Best practices
Backups and disk fault tolerance
Disk drive fault tolerance technologies, such
as mirroring and RAID-5, should never be used to replace traditional
backups. These technologies are great to ensure that you do not always
have to restore data in the event of a single disk failure; however,
they do not protect you from multiple disk failures or total server
failure. Good backups are always a must whether disk fault tolerance
technologies are used or not.
