The Arrival Of Affordable Disk-To-Disk (D2D) Storage, Part 2
by Diamond Lauffin
wwpi.com
Editor's Note: Tape vs. Disk for primary backup is a controversial area. Responses to this commentary are encouraged (mark_ferelli@wwpi.com). The first part of this article appeared in the November issue of Computer Technology Review. Click here for Part 1.
While a storage medium's performance is a very important factor, other factors must also be evaluated to determine a medium's suitability for backup/restore functions. These other factors include availability, scalability, system management and ease of use. Like any other factors in storage, certain costs and risks are associated with choices IT managers make.
TCO-The Real Cost of Storage
To fully appreciate the impact the new and affordable D2D can have on an organization's storage model, it is necessary to examine the obvious and not-so-obvious costs involved in implementing various storage solutions. To understand the true cost of any type of storage-tape, hard disk, or optical, it's necessary to consider the Total Cost of Ownership (TCO).
TCO certainly starts with hardware and software, such as servers, HBAs, RAID, tape drives, optical disks, and management applications, but also includes, among other things, the cost of managing storage (including personnel costs) and the cost of managing risk-weighing the cost of fault tolerance and availability against the cost of downtime.
The cost of managing storage is an area in which the contrast between tape and D2D is particularly clear. Tape solutions can be notoriously labor-intensive. Maintaining tape can involve such tasks as identifying and retrieving tape volumes, monitoring tape barcode sequences, loading and unloading tape, inspecting tape for wear, rotating tape, manual disaster recovery operations, and inventory management.
Of course, there are automated tape solutions-including loaders, stackers, and libraries-that can relieve some of this burden, but managing tape solutions is still plenty of work, especially compared to D2D. The large storage capacities, durability of media, fault tolerance, and highly automated management solutions associated with hard disk storage keep manual management of D2D data storage to a minimum.
The Cost of Managing Risk
The cost of managing risk is another significant component of TCO that is affected by the type of storage solution selected. Any storage solution involves some degree of risk-risk that data will become corrupted, lost, or be otherwise unavailable. An organization's choice of tape, hard disk, or optical storage dictates the type of risk to which the organization's data is exposed.
Tape has its obvious risks, including degrading and wearing out and the possibility that the medium could tear, or that a tape drive can fail to the point of damaging the tape itself. Hard disks and optical storage can crash, or suffer other technical difficulties. Because any system can be vulnerable to failure, it is essential to maintain fault tolerance for all systems-tape, hard disk, or optical. The majority of D2D systems today operate in highly reliable RAID 5 configuration, with fully redundant components that are hot swappable, with complete online preemptive monitoring for all online/on-site and online/off-site backup and disaster recovery functions.
A crucial step in avoiding equipment failure is being alerted to it before it occurs. The best way to do this is to maintain an event-oriented system that can alert managers to potential component or system failures 24/7. Sophisticated remote management tools in today's D2D systems alert managers to any problems. Web-enabled GUIs provide system configuration, event and component monitoring from any standard web browser.
The length to which an organization goes to protect its data usually depends on how critical the data is to the organization, and on the organization's financial resources. Managers must weigh the cost of fault tolerance and high availability versus the cost of downtime. The cost of downtime in some areas of financial services can be substantial-millions of dollars per hour. Though the dollar cost may not be as high, downtime can be devastating for smaller organizations, as well.
Beyond the obvious step of employing both full and incremental data backup, what can an organization do to manage risk? There are a number of topologies IT managers can consider. D2D can play a crucial role in all of them.
A Storage Area Network (SAN) can provide a very high level of availability and reliability. SANs can incorporate hard disk, optical storage, and tape media (including automated tape libraries). A SAN, of course, can be an expensive and complex system to implement and maintain. The best D2D systems support a variety of storage topologies, including SANs.
Some organizations protect their data by employing a hot disaster recovery site. In this situation, they are likely to utilize wide-area connectivity and remote backup. RAID can be an excellent choice, providing data availability and recoverability to protect non-critical applications
D2D not only supports a primary online/on-site system but also makes it possible to co-locate a secondary D2D online disaster recovery system off-site. This solution provides immediate access to data in the event of the catastrophic loss of a data center.
Combining RAID and SANs
It is also possible to use RAID and SANs together to protect data. This combination can enhance the protection provided by RAID, offering redundancy and eliminating the risk of a single point of failure. One of the traditional advantages of SCSI-based or Fibre-based disk products has been hot-swap capability and redundancy. Today's advanced D2D should offer both capabilities.
In addition to protecting data through fault-tolerant architectures, managers need to be concerned with a storage solution's capacity and scalability.
D2D systems can offer ample capacity, some starting at 160GB native/320GB compressed. Data is secured on a disk-based RAID system in a compressed format, delivering fault-tolerant unrestricted configuration options at a low cost per megabyte. Scalable systems are available that span from 160GB to multi-petabytes of online capacity.
In virtually every organization, data storage requirements are increasing dramatically every year. In many cases, storage requirements increase by 100% or more annually. D2D offers significant advantages in terms of scalability, compared to tape. With D2D, a manager can increase storage capacity with no additional application-based tape library slots or drive license charges.
Storage Virtualization
Storage virtualization can make storage management much more efficient, speeding access to files and enabling managers to optimize their use of hardware.
Virtualization in D2D environments accommodates unlimited amounts of storage efficiently. D2D provides centrally managed storage pooling and virtual volume allocations. Virtual data volumes can be dynamically created, expanded, deleted, or moved from place to place, and storage pools and volumes can be built from different physical storage devices.
D2D systems that have proprietary virtualization applications should allow configuration without interruptions, allow hot spare drives to be added and deleted either as a pool or an array-dedicated spare and data management features such as snapshots, bit-level replication and virtual tape tools.
Ease of Use
In addition to the highly automated nature of D2D, which simplifies management, D2D is easy to use in other ways, too. For example, configuration and setup can be accomplished in less than 20 minutes.
To load any type of RAID onto a system, it is necessary to have software on a server or workstation that is able to communicate with and configure the RAID system. Self-recognition features built into firmware enable a server or workstation to communicate with a RAID system and configure it.
Since an organization's storage resources do not always grow in a systematic way, it is essential to have versatile hardware. The most advanced D2D solutions are system independent, supporting SAN, DAS, or NAS configurations, and Full Fabric, Fibre, SCSI, or ATA. They provide support for TCP/IP, Ethernet, Data and SCSI over IP, and for Serial, LAN, WAN, or web connections.
These systems are also designed to be completely host- and operating system-independent (providing that the host can support external SCSI or Fibre Channel disk drives). They support Windows NT/95/98/2000, Novell Netware, SCO, Linux, MacOS, Solaris, AIX, and Unix and clustering such as Microsoft's Window's 2000 Datacenter (Cluster) Server. Internet-enabled management processors are compatible with all major web browsers.
Now that IT managers can take advantage of affordable D2D as an alternative to tape, they can enjoy hard disk performance, availability, accessibility, scalability, and ease of use for more applications than ever before. It is not likely tape will disappear as a storage medium, but in light of the price equality with D2D, the number of storage niches tape occupies should, near term and will long term, decrease significantly.
Diamond Lauffin is the executive vice president at Nexsan Technologies (Woodland Hills, CA). |
