Storage Technology Basics: A detailed explanation of storage virtualization

Simply put, virtual storage (Storage virtualization) means that multiple storage media modules (such as hard drives, RAID) are centrally managed through a certain set of methods, and all enclosures are managed in one storage pool. This can be a variety of storage devices unified management, to provide users with large capacity, high data transmission performance of the storage system, called virtual storage.

The basic concept of storage virtualization is to separate the actual physical storage entities from the logical representation of storage, where the application server only deals with the logical volumes (or virtual volumes) that are assigned to them, regardless of which physical storage entity their data is on.

The mapping relationship between a logical volume and a physical entity, is cared for by the volume management software installed on the application server (called host-level virtualization), or the controller of the storage subsystem (called the storage Subsystem-level virtualization), or the dedicated appliance (called Network-level virtualization) that joins the storage network SAN.

Both host-and storage-subsystem-level virtualization is an early, lower-level virtualization because they cannot consolidate multiple, or even heterogeneous, storage subsystems into one or more storage pools and build logical virtual volumes on them to maximize storage capacity, centralize storage, and reduce storage costs.

Only the virtualization of the network level, is the real sense of storage virtualization. It consolidates the various branded storage subsystems on the storage network into one or more centrally managed storage pools (storage pools can span multiple storage subsystems), and create one or more virtual volumes of different sizes as needed in the storage pool, and assign these virtual volumes to a variety of application servers on the storage network according to a certain read and write authorization. This achieves the goal of taking full advantage of storage capacity, centralizing storage management, and reducing storage costs.

At present, there is no unified standard for the development of storage virtualization, there are two main ways from the topological structure of storage virtualization: symmetric and asymmetric.

Symmetric storage virtual technology refers to the virtual storage Control device and storage software system, switching device set into a whole, embedded in the network data transmission path; Asymmetric storage virtual technology means that the virtual Storage Control device is independent of the data transmission path.

Storage virtualization has the following characteristics:

1, storage virtualization is a SAN inside the storage central management, centralized management, which is a feature of virtualization, a prominent place. Can get a lot of revenue, reduce costs.

2. Storage virtualization breaks the line between storage vendors, that is, you use EMC's stuff, and you have to buy EMC later, because it's impossible for him to manage what EMC does and what IBM or HDS replaces. With storage virtualization, this kind of barrier will be broken.

3, is the use of different, can be applied to different brands of high middle and low storage equipment.

Storage virtualization still cannot be separated from two broad categories of software and hardware. The division is also reflected in the distinction between storage hardware vendors and software vendors, which typically provide their own virtual storage products based on the core technologies they possess.

HP has a product in the context of host-based virtualization, storage based virtualization, and virtualization based on the network layer. Among them, storage-system based virtualization products----HP StorageWorks Enterprise Virtual array Eva is the most familiar to users. Currently, Eva series has Eva 3000 and Eva 5000 available to choose from.

The most prominent advantage of the HP Eva series is its ability to improve performance. Virtualization allows data to be distributed across multiple disks, which no longer needs to be placed in a traditional RAID group by disk capacity size and RAID protection type. HP Eva employs Vraid (virtual RAID) technology to support multiple virtual disks in a storage pool of various capacities and RAID types.

HDS's fifth generation storage System----Tagmastore Universal storage platform, while increasing storage capacity, also focuses on improving performance and cache management, ensuring quality of service in an environment that is both highly consolidated and reasonably partitioned. Tagmastore is a virtualized product based on storage devices.

The HDS Tagmastore Universal Storage Platform employs virtualization technology, with built-in virtual tiers, to manage up to 32PB of internal and external storage capacity, and to support logical partitioning within and outside storage, as well as remote replication between complex, arbitrary storage locations.

IBM's network based storage virtualization offerings are mainly comprised of San Volume Controller (SVC) and San File System. SVC is the controller of the entire SAN (storage area Network) network, which consolidates various storage devices in the San into one storage pool and allocates storage, performance, and functionality on demand. The SVC is transparent to both the server and the storage device. SVC provides a unified data replication platform for various storage devices. SVC is a software and hardware integrated product. When the SVC was first launched, the software that implemented the storage virtualization ran on a hardware device similar to a server. Today, the software can also be installed on switches in the SAN, such as Cisco's MDS network switch. SVC is designed for a fully open storage environment and can be compatible with a variety of storage devices.