Enterprise storage buyer's guide: Frequently asked questions and glossary

A concise guide to enterprise storage

Storage infrastructure modernisation, expanded server and now desktop virtualization projects, disk-based backup and archiving deployments, new file-oriented applications and Cloud-based service offerings are activities propelling new investments in storage. IT executives are showing a renewed willingness to invest in enterprise storage solutions that address the business issues of complexity, reduce expenditure and improve resource utilisation.

Enterprise storage buyer's guide:

What is enterprise storage?

Enterprise storage is a centralised storage system that businesses use for managing and protecting data. It also enables data sharing through connectivity to various computers in a network environment that includes UNIX, Windows and mainframe platforms.

Enterprise storage differs from consumer storage in a number of ways, most notably size. An enterprise solution will also take into account factors like scalability, redundancy, backup, archiving and disaster recovery.

What are the different types of enterprise storage solutions available today?

There are a number of different systems including direct-attached storage (DAS), network-attached storage (NAS) and storage area networks (SANs).

What is direct-attached storage?

DAS is directly connected to the host computer and access to the data is provided through the organisation’s local area network (LAN). DAS has its limitations and can impact the rest of the data network but is generally the basic building block on which SAN and NAS can be deployed. The storage devices that are used to develop a DAS storage subsystem include SCSI, PATA, SATA, serial-attached SCSI (SAS), fibre channel (FC), flash and RAM.

On the plus side, DAS requires low initial investment. Additional storage capacity can be added as required and the complexities of networked storage are avoided.

What is network-attached storage?

A NAS device is a server capable of delivering storage across a LAN. It can take the form of data servers directly integrated into the LAN architecture. Enterprise storage usually consists of a mixed storage environment that includes DAS, NAS, and SAN. In a NAS/SAN convergence, NAS offers reliability features such as RAID (Redundant Arrays of Independent Disks) and enterprise and data protection features such as replication and mirroring.

What is a storage area network (SAN)?

A SAN is the most widely used enterprise solution used today. It allows an enterprise to connect more than one host to a storage device. This enables server computers to systematically control the storage volume in a storage device. SANs offer a host of compatibility advantages with respect to applications and much greater functionality.

What is a scale-out disk storage system?

Scale-out disk storage systems are built from storage nodes that are interconnected to each other via an internode switch. This switch is usually a dedicated Ethernet or InfiniBand switch. The storage nodes are built using industry standard x86 servers with internal direct-attached disks.

What are the benefits of scale-out disk storage?

The magic of scale-out disk storage systems is in their array software, which implements system functionality, protection from disk or node failures and the ability to scale linearly until the internode switch bottlenecks on input/output operations per second (IOPS) or bandwidth.

Scale-out storage has traditionally been popular in high performance computing environments. IT research firm Gartner says the price differential between scale-up and scale-out is currently favouring scale-out storage, largely because of its broader use of commodity components.

How does scale-out storage differ to networked storage?

Some CIOs claim that scale-up SANs only scale to a certain point. It is rarely possible for a single disk system to scale-up to the extent of meeting all the storage needs of an enterprise. There are also fears that a single system runs the risk of availability issues and system failure.

Scale-out storage generally costs less than high end scale-up disk systems on a dollars-per-terabyte basis and delivers better price to performance ratios. However, this does not mean that scale-out storage is applicable for all applications. Gartner says in many environments, companies should consider scale-up and scale-out approaches in combination.

Enterprise storage buyer's guide: Glossary of terms3h>

FCoE: Fibre Channel over Ethernet

HDD: Hard disk drives

MAID: Massive Array of Idle Disks

NAS: Network-attached storage

OLA: Operating level agreement

QoS: Quality of service

RTO: Recovery time objectives

SATA: Serial Advanced Technology Attachment

SCSI: Serial Attached Small Computer System Interface

SAN: Storage area networks

SLA: Service level agreement

SRM: Storage resource management

TCO: Total cost of ownership

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