Practical application of the SNIA Shared Storage Model
An excellent example of this practical application of the model is provided
by the IT staff of Carlson Companies. Carlson Companies is one of the
largest privately held companies in the United States, with more than
180,000 employees in more than 140 countries. Its IT division, Carlson
Shared Services, acts as a service provider to its internal clients and consequently
must support a spectrum of user applications and services.
In formulating a global IT strategy for networking and storage, the Carlson
storage architects began with their current applications and the supporting
server/storage infrastructure. Originally, Carlson's business applications
were supported on a combination of direct-attached storage arrays and internal
storage. As shown in Figure 7, database applications ran on servers
attached to large storage arrays, and other applications ran on servers with
internal storage.
Overlaid on the SNIA Shared Storage Model, Carlson Companies' original
storage configuration clearly demarcates which applications access data
via records, which via files, and which via device-level block aggregation or
host-supported block aggregation. The first step in determining which applications
might be better served by shared storage and which shared storage
technologies are most appropriate for specific upper-layer applications is to
diagram the upper-layer applications and their storage access methods.
By using the Shared Storage Model, the storage architects clarified the
relationship between application requirements and storage resources and
also revealed the administrative overhead incurred by dedicated storage
units. The system required four large storage frames and six additional
arrays to support Carlson's data center applications. Each storage unit
required separate administration as well as maintenance contracts from the supplying vendor. Because storage consolidation is one of the key benefits of
SANs, the Shared Storage Model offered a framework for modifying the
components in the block subsystem to reduce the number of storage devices
while still serving Carlson's business applications.
Figure 7
As shown in Figure 8, analysis of Carlson's former storage deployment
led to a proposed shared storage configuration that leveraged both SAN and
NAS technologies to streamline storage administration and enable more efficient
use of storage capacity. This design replaces the four large directattached
storage frames with a single SAN-attached storage array supporting
more than 10 terabytes of data. In this example, Oracle and other Carlson
custom applications now share a single, highly available storage resource that is more easily administered and offers more economical maintenance
support compared with the four direct-attached storage frames it replaced.
Shared directories and other internal applications have moved from
direct-attached, dedicated storage to large NAS filers. In this instance, NAS
was chosen for its cross-platform support and for its ability to serve remote
NAS access for Carlson clients. Infrastructure applications that have no compelling
reason to reside on either NAS or SAN remain on internal storage, as
shown on the right side of the diagram.
Figure 8
Remote storage access is also a significant factor for organizations with
geographically dispersed sites. In Carlson Companies' global IT strategy, safeguarding corporate data generated at remote locations is essential for
business continuance. Relying on each remote office to back up its own data
locally offers no guarantee that backups are successfully completed or that
data can be restored in the event of failure. Consequently, Carlson decided to
streamline backup operations by bringing remote backup operations into its
central data center.
As shown in Figure 9, the Shared Storage Model is used to define four
separate remote office backup scenarios. Remote offices with no local file
servers have valuable corporate data on internal drives of laptops and desk
workstations. Typically (and unfortunately) for most enterprise networks,
this data is rarely backed up, resulting in loss of productivity if a laptop or
desktop disk drive fails. For these sites, Carlson uses software that enables
block change backup, meaning that only the data that has changed since the
last backup is sent to the data center backup facility. This arrangement
reduces the amount of data that must be sent across the wide area network and accomplishes the goal of securing dispersed corporate data assets. Similarly,
remote sites with a local file server can be backed up using block
changes, again reducing the amount of traffic generated over the WAN.
Figure 9
In the remaining two scenarios, a remote office may have a local NAS or
SAN installed. For NAS, Carlson is leveraging vendor-supplied file backup
utilities to replicate data from the remote site to the data center NAS equipment.
At the data center, the NAS-based data can then be centrally archived
to tape. For remote SAN installations, Carlson is using IP storage technology
to transfer locally generated Fibre Channel SAN data to the corporate SAN.
In Carlson's case, the data center SAN is built with an IP SAN core, thereby
facilitating IP-based block backup between remote and central SANs.
For Carlson Companies, the SNIA Shared Storage Model offers a coherent
framework for analyzing current and future storage requirements for both
the data center and its dispersed remote locations. For storage architects, the
Shared Storage Model is a tool for defining application and storage relationships
while enabling drill-down to more detailed storage-specific issues. For
CIOs and IT executives, the model provides a basis for understanding the
composition of their storage deployments and seeing how proposed acquisitions
contribute to broader strategic IT goals. Additional information on the
SNIA Shared Storage Model is available in Appendix E as well as the SNIA
Web site at www.snia.org.
Designing Storage Area Networks: A Practical Reference for Implementing Fibre Channel and IP SANs, 2nd Edition was written by Tom Clark and published by Addison Wesley Professional. Did you find this book helpful? Purchase it directly from the publisher.
