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Until quite recently it was accepted practice that in most
deployment scenarios, storage devices were an integral part
of the server hardware.
Each disk device was specified with excess capacity so as
not to impact performance or bring operations to an unexpected
halt. To specify too little capacity at rollout meant to incur
downtime for hardware upgrades later. This led to the installation
of an abundance of dedicated, sometimes vendor-specific storage
which whilst carrying unused capacity, was unable to be shared
with other systems that might require additional resource.
SAN (Storage Area Network) technology presented the foundation
for creating and managing large pools of centralised, multi-purpose
storage rather then a mass of directly attached or internal
devices. It opened the way for significant cost savings through
improved storage utilisation, simplified storage management
and lower IT support and training costs.
Traditional proprietary SANs have been deployed out of necessity;
the enterprise infrastructure has had too much to gain from
the flexibility they represent not to adopt them but too little
by way of product choice. With hardware-centric solutions,
the high acquisition cost of even a unit of modest sise has
been exacerbated by vendor lock-in for capacity and feature
upgrades. Early adopters now looking to upgrade their SAN
purchase can fully expect to find it has been deprecated in
favour of the “latest and greatest” - additional
capacity or new feature-set requirements cannot be met without
forklift upgrade or disproportionate cost.
Storage Virtualisation is to the SAN as Server Virtualisation
is to the server farm. Application-layer software, running
on top of generic server hardware and operating systems, is
used to abstract underlying hardware storage resources into
a logical pool of storage. Near-line quality SCSI or SATA
hard disks either internally connected or in external storage
shelves provide the actual storage resource. The virtual storage
pool can be apportioned and allocated (often dynamically)
as required to service the requirements of the server infrastructure.
Advanced functions associated with SANs such as controller
mirroring and synchronous replication features for high-availability,
or snapshots for backup, are implemented fully in software.
Since the Storage Virtualisation layer runs on standard WIntel
server platforms and largely uses point-and-click GUI management
the existing skills and experience of IT support staff are
leveraged. A performing and robust iSCSI / FC SAN solution
can be established at a small proportion of the cost of an
equivalently featured hardware SAN device. With many IT departments
already seeking to reduce cost through consolidation, the
repurposing of residual server hardware as storage servers
is particularly attractive. Where additional capacity or new
feature sets are required at a later time these can usually
be added as a matter of licensing, without attracting either
additional hardware costs or production down-time.
Virtualised Storage is a perfect partner to Server
Virtualisation. It allows the same benefits of better utilisation
and lower operating costs to be realised for storage resource
as can be achieved for server assets. Pairing Server Virtualisation
with Virtualised Storage also delivers the most advanced and
important benefits of virtualisation, including the ability
to move virtual machines transparently between physical processors
and entire physical servers. With this comes vastly improved
scope for zero-downtime maintenance, dynamic resource re-allocation
and fault-tolerance over traditional architectures.
As the volume of data held and processed by businesses will
only increase, choosing the right storage infrastructure will
continue to be an important factor for IT investment planning
for the foreseeable
future.
| Virbis
Storage Virtualisation Product Portfolio
Virbis is an authorised solution centre for Storage
Virtualisation products from market-leading vendors,
including DataCore and HP. We offer a wide range of
consulting, design, engineering and troubleshooting
services for these products, all of which are delivered
by vendor-trained and accredited staff.
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