Storage Management Simplified with Virtualization

Storage Management
Simplified with
Virtualization
magine a world where storage management is simplified; everything works together;tIhere are no configuration issues when upgrading, and vendors all cooperate to allowinformation to be easily stored and retrieved seamlessly. This was a reality in themainframe world, but the deployment of open systems shattered these concepts.Today, most storage array vendors are more focused on selling their own arraysversus creating a solution that is easy and cost effective to manage.
One proposed answer to these incompatibility and storage management challengeshas been virtualization. Virtualization, in simplistic terms, creates logical views of thephysical storage; it makes the storage appear to be one large identical storage pool.With virtualization, a user no longer needs to know how storage devices are configured,where they are located, or what their capacity is. Users can then take advantage ofcompetitive pricing and purchase their storage from multiple vendors transparentlyutilizing additional capacity as needed.R
E Today, storage virtualization can occur at multiple levels such as at the device level andP volume level (see Table 1). The key element in each case is how the virtualizationA system maps the logical presentation to physical devices, and where this mapping isP maintained and controlled. Other factors include performance, interoperability, and scalability issues. For example, network (SAN fabric based) virtualization is the mostE scalable and array (storage based) virtualization has interoperable constraints.T
I TABLE 1: VIRTUALIZATION DEFINITIONSH
W
Virtualization Type Definition
The first type of virtualization available in the market and the most common; itwas not initially defined as a virtualization solution but a volume managerand/or file system. Host-based virtualization requires a software program to beinstalled on each host that intercepts requests for the file system or the logicalHost Based volumes and maps it to one or more devices attached directly to the host (ormaps it via a SAN). A typical example is Veritas' Volume Manager (VxVM) andFile System (VxFS) running on the host, which can be controlled by a central SANmanager.Another common type of virtualization. It works only on storage arrays suppliedby a single vendor. The storage system presents a logical view or a volume-levelStorage System view to the user, allowing a set of physical drives to be presented as a numberBased of different capacity devices. Examples of this are IBM's Virtual Tape Server,StorageTek's Iceberg Disk System (for MVS), XioTech's Disk System, and EMC'sSymmetrix, which present virtual storage volumes or logical devices.The most recent advancement in virtualization technology. Network-basedvirtualization is transparent to the host and the host bus adapter (HBA). TheNetwork Based server's request for volumes is intercepted in the network and is redirected to aphysical storage device. Currently, two examples of this type of virtualizationexist: in-band (synchronous) or out-of-band (asynchronous).
Page 1Virtualization Constraints
All virtualization solutions available today have some constraints such as interoperability,performance and capacity (see Table 2). This point is made by Fred Moore in 101Storage Solutions. "Presently, virtualization at the SAN and NAS level doesn't effectivelymanage the capacity, performance, and inefficiency issues at the individual storagedevice level."
Also, virtualization solutions expect that classes of storage LUNs be already provisionedand available for mapping by the virtualization layer, much like a volume manager. Ifno LUN exists for that class, you need to exit the virtualization appliance and provisionthe LUN mapping it back to the appliance.
TABLE 2: VIRTUALIZATION CONSTRAINTS
Virtualization Type Constraints
Does not provide path virtualization.
Most virtualization at the volume level requires flattening the SAN fabricHost Based because it optimizes the storage allocation and not the network paths.
Does not exploit the vendor-specific features of different storage devicesand systems.Does not provide path virtualization.
Storage System Does not provide scalability outside of the vendor's devices.Based Does not exploit the vendor-specific features of different storage devic... [download for more]