Storage virtualization: It’s ready, are you?


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Storage virtualization products

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Virtualization has become an essential function for storage provisioning and is included in some form with most midsized and larger storage systems. While there are many differences between arrays and their virtualization technologies, the majority of these device-based implementations don’t support disk capacity from other manufacturers. Instead of listing the large number of these storage systems, we’ll focus on the smaller category of heterogeneous storage systems. The following are examples of heterogeneous storage virtualization as implemented in hardware and software products available from a variety of vendors.

DataCore Software Corp.’s SANsymphony is a network-based, in-band software product that runs on commodity x86 servers. It supports heterogeneous storage devices via FC, Fibre Channel over Ethernet (FCoE) or iSCSI, and connects to hosts as FC or iSCSI storage. Multiple-node clusters can be created to scale capacity and provide high availability. The system provides remote replication and storage services like synchronous mirroring, CDP, thin provisioning and tiered storage.

EMC Corp.’s Invista is an out-of-band software solution that runs on a pair of servers (called a Control Path Cluster or CPC) and interacts with “intelligent switches” from Brocade or Cisco. It can virtualize storage from most major vendors, connecting to storage and host servers via Fibre Channel. Invista provides mirroring, replication and point-in-time clones between storage arrays.

FalconStor Software Inc.’s Network Storage Server (NSS) is a network-based, in-band appliance that connects to heterogeneous storage systems via iSCSI, FC or InfiniBand, and supports host connectivity with Fibre Channel or iSCSI. Expansion and high availability are provided by connecting multiple controller modules. Besides WAN-optimized replication, NSS also provides synchronous mirroring, thin provisioning, snapshots and clones.

Hitachi Data Systems’ Universal Storage Platform V (USP V) is a tier 1 storage array system that also provides in-band heterogeneous connectivity to most major storage vendors’ arrays. It includes the kinds of features and services expected from a tier 1 solution, including thin provisioning of internal and externally attached storage.

IBM’s SAN Volume Controller (SVC) is a network-based, in-band virtualization controller that sits on the SAN and connects to heterogeneous storage systems via iSCSI or FC. Pairs of SVC units provide high availability, and up to eight nodes can be clustered to scale bandwidth and capacity. Each SVC module features replication between storage systems and a mirroring function between local or remote SVC units.

NetApp Inc.’s V-Series Open Storage Controller is an in-band virtualization solution that’s very similar to a NetApp filer controller, but configured to support heterogeneous storage arrays. It connects to a FC SAN on the back end to consolidate as much storage as desired from existing LUNs, and pools them into NetApp LUNs for block or file provisioning as would a regular NetApp filer.

NetApp recently acquired the Engenio Storage Virtualization Manager (SVM), a network-based, in-band virtualization controller that supports heterogeneous storage systems. Details of how NetApp will market this solution have yet to be announced.

Handle with care

Because most storage virtualization products are in-band, care should be taken to understand the effective performance of the virtualization appliance or cluster as this will be the gating factor to capacity expansion. In addition, storage services or features will also consume CPU cycles, further reducing effective capacity.

Storage virtualization is a powerful tool to reduce Capex by improving capacity utilization or performance, but its biggest benefit may be on the Opex side. It can simplify storage management, even across platforms, and reduce administrative overhead. Virtualization can also make storage expansion a relatively simple operation, often done without taking storage systems down or disrupting users.

BIO: Eric Slack is a senior analyst at Storage Switzerland.


This was first published in August 2011

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