The Storage Application: A Fourth Generation Storage Device
Storage devices have developed over basically three generations:
In the first generation, file systems communicated directly with individual physical devices (such as floppy or hard disks).
In the second generation, arrays were created and the file systems or applications communicated with RAID controllers instead of individual disks.
In the third generation, a virtual abstraction of RAID was introduced and the file systems communicated with Virtual Volumes instead of directly with RAIDs.
This paper suggests that a fourth generation is emerging, whereby file systems will communicate with Storage Applications that will react as storage devices. Fourth generation storage devices are software elements rather than physical or even virtual devices. They are not dependent on the specific file structure of the data. Fourth generation storage devices enable the Operating Systems and the File Systems to communicate with storage in a software-to-software manner rather than software- to- device manner, with all the advantages that such a mode of communication provides.
Why a Fourth Generation Device
The need to properly manage the enterprise storage resources is becoming more and more apparent to all organizations. Users are already willing to pay significant premium for what they perceive as a manageable storage system.
Vendors of various hardware components in a Storage Area Network (HBAs, switches, RAID controllers) know they must provide ways to manage and control them. Until now, there have been few standards for this and the management tools and methods have been specific to each device and vendor. This includes tasks such as creating LUNs and their RAID characteristics and sizes, defining switch zoning, specifying LUN access control, etc.
The addition of Virtualization does not completely eliminate the need to configure all of
these components, but provides a layer of management that is uniform and independent
of various vendors. Thus LUNs created on various storage devices can be assigned to
Storage Pools and allocated as needed to server and applications. Beyond basic volume
management, the general capability to create point-in-time snapshot images of virtual
volumes using "copy-on-write" technology is also essential
This paper suggests that the storage virtualization component is a key platform for
creating high-value storage components that can be used to increase the return on the
storage area network investment. In short, the value of these fourth generation devices is
greater than the sum of the parts that make them up.