Install Windows Server 2012 R2 - MCSA Windows Server 2012 R2: Installation and Configuration Study Guide - page 34

Fault tolerance (RAID) is discussed in detail in the “Redundant Array of
Independent Disks” section.
Now that you understand what storage spaces and storage pools do, let's take a look at
some of the other advantages of using these features in Windows Server 2012 R2.
Availability One advantage to the Storage Spaces technology is the ability to fully inte-
grate the storage space with failover clustering. This advantage allows administrators to
achieve service deployments that are continuously available. Administrators have the ability
to set up storage pools to be clustered across multiple nodes within a single cluster.
Tiered Storage The Storage Spaces technology allows virtual disks to be created with a
two-tier storage setup. For data that is used often, you have an SSD tier; for data that is not
used often, you use an HDD tier. The Storage Spaces technology will automatically transfer
data at a subfile level between the two different tiers based on how often the data is used.
Because of tiered storage, performance is greatly increased for data that is used most often,
and data that is not used often still gets the advantage of being stored on a low-cost storage
option.
Delegation One advantage of using storage pools is that administrators have the ability to
control access by using access control lists (ACLs). What is nice about this advantage is that
each storage pool can have its own unique access control lists. Storage pools are fully inte-
grated with Active Directory Domain Services.
Redundant Array of Independent Disks
The ability to support drive sets and arrays using Redundant Array of Independent Disks
(RAID) technology is built into Windows Server 2012 R2. RAID can be used to enhance
data performance, or it can be used to provide fault tolerance to maintain data integrity in
case of a hard disk failure. Windows Server 2012 R2 supports three types of RAID tech-
nologies: RAID-0, RAID-1, and RAID-5.
RAID-0 (Disk Striping) Disk striping is using two or more volumes on independent disks
created as a single striped set. There can be a maximum of 32 disks. In a striped set, data
is divided into blocks that are distributed sequentially across all of the drives in the set.
With RAID-0 disk striping, you get very fast read and write performance because multiple
blocks of data can be accessed from multiple drives simultaneously. However, RAID-0 does
not offer the ability to maintain data integrity during a single disk failure. In other words,
RAID-0 is not fault tolerant; a single disk event will cause the entire striped set to be lost,
and it will have to be re-created through some type of recovery process, such as a tape
backup.
RAID-1 (Disk Mirroring) Disk mirroring is two logical volumes on two separate identi-
cal disks created as a duplicate disk set. Data is written on two disks at the same time; that
way, in the event of a disk failure, data integrity is maintained and available. Although
this fault tolerance gives administrators data redundancy, it comes with a price because it