Virtualization's new voice: virtualization plays an important role in an overall data management strategy - Storage Management

Computer Technology Review, Feb, 2004 by Gabriel Lopez

Virtualization seems to have made a comeback of sorts lately. Only four short years ago, "storage virtualization" was viewed as the ultimate solution for managing storage. But as a core technology in and of itself, the buzz quickly evaporated. The downfall of virtualization seemed just as fast as its ascent in the storage industry.

But listen carefully as whispers of virtualization are getting louder. The current reality is that when spoken in conjunction with enabling storage services such as replication, mirroring and rapid data recovery, virtualization has a new voice and serves as a key enabling factor for the proliferation of data services in an environment with a heterogeneous operating system and multiple storage devices. Virtualization can play a vital role in overall data management strategy. This article will examine the factors behind the renewed attention being paid to the virtualization story and why that attention is justified when used in conjunction with storage services.

Virtualization is not all it's cracked up to be, without the proper framework. Clever "virtualization" technology masks the differences in storage hardware and presents a unified way to interact with disk/tape devices from different manufacturers.

The true value of virtualization can only be realized within a full-featured storage solution that leverages a customer's current IT infrastructure and provides not just virtualization but top performance (fast data storage and access), ease of use, unified SAN and NAS management, virtualization across cabinets (not just within one storage cabinet), and seamless support of heterogeneous storage environments. For a virtualization solution to make business sense, it must offer total freedom of choice in device vendors, interfaces, connectivity, platforms and protocols.

But where does it make sense to virtualize? Disk-level virtualization is limited to specific vendor devices and, at the application host-level, it can be seen as a synonym for volume management--host-based, operating system-specific, and with a point of control on every single machine on the network. Ideally, storage virtualization has no operating system specificity and can be managed centrally, rather than from each host in the environment. A true virtualization model cuts across vendor barriers.

The most effective location for virtualization is in the storage network. By interjecting a layer of intelligence between servers and storage, network-based virtualization offers the most freedom from operating system constraints and vendor-specific storage devices. It is also completely centralized, as the intelligent "nodes" can be managed from a single point of view.

A well-architected "network-based" storage infrastructure software should be able to virtualize the disk and/or tape storage from multiple vendors, provision the virtual disk to the host-attached Fibre Channel/iSCSI/CIFS/ NFS network while provisioning the virtual tape to hosts attached to the Fibre Channel and iSCSI networks, and associate mission-critical storage services (replication, snapshot, backup, HSM, etc.) to the logical disk and/or tape. It should be so seamless that an ISV developing an application in Windows does not have to worry about the underlying storage devices or protocols.

As another example: With virtualization, good RAID software should present a logical disk (RAID-0 or 1 or 5, etc.) to the upper layer, and allow the user to employ the SCSI/Fibre Channel/ATA/SATA disk from any manufacturer; smart RAID software should enable the application/administrator to expand or shrink the logical disk on-the-fly, and be able to perform snapshot, replication, backup, etc., in real time without affecting the upper layer application; and a network-based, intelligent RAID software should be able to offer "logical disk" but also "logical tape" and allow the application host to access the logical disk through the Fibre Channel/ iSCSI/CIFS/NFS network and the logical tape through the Fibre Channel/iSCSI network.

Significant Benefits in Data Management

Built on a solid foundation, virtualization offers significant benefits in data management. Implemented effectively, virtualization offers a layer of abstraction above the physical layer of disks and spindles. The issue with the physical layer is that it varies from vendor to vendor, and even between device models from the same vendor, making storage provisioning quite a challenge. A virtualization solution unifies everything (RAID and JBOD, iSCSI, SCSI and Fibre Channel) and makes it all look the same. In short, it provides a utility model for storage. Disk space is carved out of a pool and assigned to servers without any need to physically touch the servers.

What storage virtualization brings to the table is a way of incorporating storage services into the network, without any reliance on operating system or storage-specific tools. This is the true business benefit, and what many end users are beginning to realize.