Storage area network (SAN) deployments deliver high-performance
block-based storage to transaction-centric applications.
Network attached storage (NAS) systems provide shared access to
file-based applications. These are very different types of storage,
with different features that serve different business needs. In the
past, SAN and NAS existed as separate entities within the
enterprise, but this is changing. Smaller organizations can benefit
from the performance of SAN technology, while large enterprises can
use NAS and SAN together, tailoring and tiering storage to obtain
the best value for users and applications. (See
NAS Explained for more background
information on NAS.)
Today, SAN and NAS platforms routinely exist side by side and
can often be interconnected with each other in order to share their
respective benefits. A NAS gateway can bring NAS functionality to
the SAN, allowing the gateway to serve files. In other cases, you
may find converged storage platforms providing both a SAN and NAS
interface and allowing the storage platform to operate in either
environment. However, NAS integration is not always appropriate and
storage administrators must use care when connecting SAN and
NAS.
Best Practice No. 1: Examine the extent of, and need for,
convergence
The choice to integrate (and how much to integrate) should be
driven by your particular storage needs and convergence goals. A
SAN-centric environment with relatively light NAS needs would
benefit from a file server connected to the SAN through a NAS
gateway. Conversely, a NAS-heavy environment with a limited SAN
deployment may benefit from eliminating the SAN entirely. Experts
note that applications, like Exchange or an Oracle database
management system, can potentially run fine from NAS. When the mix
of NAS and SAN is closer to 50/50, don't be afraid to maintain
separate infrastructures or limit the level of integration between
the two infrastructures.
Practice No. 2: Consider the availability of multiprotocol
storage systems
The storage industry is moving toward a single system that can
support both file and block access. This type of system, which is
often called multiprotocol or
unified storage, allows applications to use
file systems for storing data and perform block-based I/O. NAS
gateways are likely to be the preferred choice to merge separate
NAS and SAN systems that are already deployed in the
infrastructure. However, unified storage platforms may be
preferable when integrating NAS and SAN in new deployments,
colocation facilities or regular technology refreshes.
Practice No. 3: Ensure that storage management tools can
handle a mixed environment
Any NAS/SAN integration should include an examination of
management tools to handle administrative tasks within a mixed
storage infrastructure, such as resource allocation and data
migration. The objective is to simplify management tasks by
reducing the number of tools, but it's important to test any tools
in advance. "We're seeing more multiprotocol storage," says Greg
Schulz, founder and senior analyst at the Storage IO Group. "But if
you're coming through a NAS device for block-based storage, you
might be paying a performance penalty in exchange for all those
management features."
Practice No. 4: Opt for systems that minimize
disruption
Emerging storage systems are more tolerant of changes and
additions, but disruptions can still occur. When merging NAS into a
SAN, it's important to gauge the impact of storage changes on
performance or availability. Ideally, adding or redeploying storage
should result in minimal (if any) disruption, but it will
ultimately depend on your storage infrastructure and application
demands. Once the effect of change is understood, you can modify
internal practices to streamline the change process.
Practice No. 5: Ensure that necessary features are added or
maintained
Bringing two disparate storage platforms together does not
guarantee that similar features will work together or that a
feature available in one platform will be available in the other.
For example, a SAN storage infrastructure may support storage
tiering, but NAS might not support tiering. Verify that necessary
features are available and continue to operate together.
Practice No. 6: Seek out newer NAS gateways that offer high
availability and scalability
Older NAS gateways cannot provide high availability or
significant capacity scaling because they were tightly coupled to
the data being processed. This prevented multiple gateways from
accessing the same files within a given pool of storage. Clustering
and metadata server schemes could work around these issues and
allow simultaneous file access, but this usually added complexity
and cost to the NAS gateway. Use NAS gateways that can access the
same files simultaneously. This supports load balancing for better
performance and failover capabilities for high availability, two
valuable enterprise features when using multiple NAS heads. Also
opt for NAS heads that can support expanded file services on the
SAN, often by integrating the NAS file system with the SAN volume
manager. Otherwise, the NAS remains a logical "island" even though
it may be physically interconnected with the SAN.
Practice No. 7: Be concerned with data protection
capabilities
Older NAS gateways cannot generally perform advanced data
protection tasks, such as looking into a SAN fabric to execute
snapshots or replicating file volumes across the SAN. Look for NAS
heads that provide native data protection features that can
interoperate with the SAN. These features are already available
through software tools. For example, EMC Corp. NAS gateways, such
as the Celerra NS family support standard backup software, such as
EMC NetWorker, Symantec Corp. NetBackup, CommVault System Inc.
Galaxy, Hewlett-Packard Co. (HP) OpenView, Atempo Inc. Time
Navigator or IBM Tivoli Storage Manager (TSM). The Celerra gateways
also include data protection software tools ,such as Celerra
FileMover for archiving and Celerra Replicator for file
replication.
Practice No. 8: Look for advanced file services in the NAS
gateway
Intelligent policy features, such as those seen in storage
resource management (SRM) tools, are emerging in NAS gateways --
using policies based on file metadata, such as date, location,
business group and access frequency.These criteria allow file data
to be moved to its appropriate location on the SAN, then be
migrated, replicated, or staged for backup. Experts suggest that
such features should ultimately be integrated with SRM tools for
infrastructure-wide provisioning, capacity planning and data
protection capabilities. For example, a converged NAS/SAN system
might migrate infrequently used files to nearline disk but perform
the migration as a background, rather than a manual task.