Storage Provisioning and Networking - Deploying and Managing a Cloud Infrastructure - page 249

of accessing may entail consuming or using a resource. Authorization is the act of granting
physical or virtual access permissions to a person for consuming or using one or more com-
puter resources.

Understanding SAN and NAS

A SAN is a dedicated network that provides access to consolidated, block-level data storage.
SANs are primarily used to make storage devices, such as disk arrays and tape libraries. NAS,
on the other hand, is file-level data storage that is connected to a network of heterogeneous
computer systems. NAS is often manufactured as a computer appliance and used for special-
ized purposes. NAS is often compared to SAN because of its ability to behave as both data
storage and a file server (see Figure 9.2).
To conceptualize this, think of SAN storage appearing as a local disk on a computer to
which a SAN is attached. This enables the host computer to fully control the SAN storage
(disk/volume management). NAS only appears as a file server providing block storage capa-
bility and thus allows only a limited number of nonadministrative operations from the host
machine.

FIGURE 9.2 SAN vs. NAS

SAN
Block storage

NAS
NFS/AFS clients

Network file server

Both of these systems were designed as high-speed on-premises solutions. However, as
services and applications move into the cloud, the requirement or need for an on-premises
data center diminishes almost completely. Locating storage close to the services that con-
sume data from those storage sources is far better, both technically and administratively,
than having to maintain two separate environments.
One of the basic intentions of the cloud was to make different hardware components
act and behave as a large but single entity. The applications and services running on top of
such a platform should be unconcerned about their physical location as well as the physical
location of the data and other applications and services they are accessing or using.
However, to take complete advantage of the cloud platform and bypass network
latency and performance lag, both logic and data should be placed in a consolidated cloud