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December 05, 2008
Storage Virtualization: Everybody in the Pool
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Relatively speaking, storage virtualization is a simple concept: take a bunch of networked storage devices and (magically?) turn them into one big storage device that can be managed from one central control tower. As a result, heterogeneous storage environments are easier to manage (at least theoretically), administrative tasks can be streamlined, data can be migrated quickly, and there is more efficient use of disk space, among other benefits.
These features help to explain its popularity. As with anything promising simplicity and lower capital expense, there is growing interest in storage virtualization. According to a survey commissioned earlier this year by F5 Networks, the percentage of U.S. enterprises implementing storage virtualization will jump from 21 percent to 47 percent in the next few years. European adoption will jump from 37 percent to 61 percent.
Nothing is as simple as it seems, though, as there are many paths to take from piles of disks to one big, happy pool. Storage virtualization can be implemented and discussed in several different ways -- maybe three, maybe four, possibly five -- depending on how you look at it and whom you ask. Some basics might help.
Broadly speaking, there are two types of storage virtualization: block and file. Block is most common, embodied by SAN or NAS technologies, where distributed systems look like one storage device. File virtualization takes place “in front of” the storage network, usually in an appliance of some type.
More often, you’ll hear talk of the implementation methods. Host-based virtualization refers to software on a server providing the virtualization layer and creating the one big drive effect. Appliance-based virtualization puts a hardware device on the storage network. Network-based virtualization works at the switching level.
Some people use other terms to describe the same scenarios. In-band virtualization means the virtualization occurs in the data path between the host server and the storage units, as with an appliance. Out-of-band means the virtualization is outside the data path, at the switching level. Split-path virtualization combines in- and out-of-band and typically involves software services or an adapter in a switch or appliance.
Some people reduce the discussion further to appliance-based virtualization versus network-based. Appliances are easy to use, proponents say. But, says the other side, they can add a bit of latency. The network approach can be more flexible and scalable, fans say, but others counter that it is more complicated to implement. It could come down to a matter of where you prefer to manage storage. It could come down to preferring a particular vendor and not caring at all about bands.
If you’ve got a favorite storage brand, chances are it has a virtualization solution. This includes both big server vendors -- like IBM, HP and Sun -- and storage leaders. EMC offers a range of block- and file-virtualization products, including Invista, which virtualizes SANs using a split-path approach, and virtualization consulting services. LSI’s StoreAge SVM (Storage Virtualization Manager) is a SAN appliance that provides virtual volume management in heterogeneous environments.
Last month, HP introduced the StorageWorks SAN Virtualization Services Platform (SVSP), a split-path, switch-based platform built on LSI’s SVM and that will operate across HP and non-HP storage arrays, the company says. Observers commented that SVSP will compete with IBM’s network-based SAN Volume Controller, which is designed to combine storage from multiple disk systems into one shared pool.
Hitachi Data Systems integrates virtualization into its enterprise disk arrays. One of the best-known developers of virtualization appliances is NetApp, whose V Series devices can scale up to the terabyte and petabyte ranges of storage using heterogeneous hardware. There also are tools from software developers. DataCore SANsymphony software turns physical disks into SAN-accessible virtual disks.
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There are 2 discussion items posted.
Himangi, TOVirtualization
Submitted by himangim on 12/05/2008 - 3:29AM
Good and Very informative article! very useful for beginers... liked it..
Himangi,
Times Of Virtualization
Post #1
