Selecting a Data Storage System

Answer the following questions to determine a storage system that best meets your needs:

How much data do you currently need to store?

If a very large amount of data must be stored, a tape-based storage system might be your best choice. The media cost per megabyte is significantly lower for tape than it is for many other types of storage media.

What are your projected data-storage needs?

The storage needs of many organizations double every year. Consider purchasing a larger storage system than is necessary to satisfy present requirements or a scalable system that you can expand as your needs grow. To evaluate how this might affect your situation, compare your data storage from several years ago to your current levels, and use this growth to estimate your future needs.

How many users or applications simultaneously access the data storage system?

Most vendors offer multidrive systems that allow several drives to be accessed at once. In this way, multiple users or applications can simultaneously access the system without affecting performance.

How important is data-access time?

If your library is used primarily to access data for real-time use, then this is your most important issue. CD-ROM disc-based solutions usually work best if data-access time is your primary concern because the random-access capability of CD-ROM discs reduces seek time to a minimum. Data-access time has two parts: seek time and transfer rate. The disadvantages of this solution are in speed and cost: the data transfer rate can be slower than tape-based systems unless the latest high-speed drives are used; and the cost per megabyte is greater than tape media.

How important is the data-transfer rate?

If your data storage system is used primarily for archiving and backing up data, then the data-transfer rate is your most important issue. If this is the case, then a tape-based solution might be best because the data-transfer rate of tape drives is approximately ten times the speed of CD-ROM disc-based drives. Tape-based systems are also less expensive per megabyte. The disadvantage of tapes is that file-access time is increased by as much as several minutes because file access is linear.

What is your budget?

Again, before you decide how much you can afford to spend, factor in the potential costs of lost or corrupted data and downtime due to problems with unreliable hardware. If the type of data that you store is important to your organization, these risks might not be worth the savings gained by purchasing an inexpensive solution.

Also, consider the whole cost. Certain hardware can be relatively inexpensive to acquire but the cost per megabyte is expensive. This is generally true for CD-ROM disc-based systems. It is also common to spend more money over time on the media than on the initial hardware.

To help you select a storage system, try creating two or more models that present different hardware and software solutions for varying degrees of storage capacity and data protection. Be sure to project for planned growth.

Table 19.1 shows the relative capabilities of possible hardware and software storage solutions: a 5 indicates this is the best available solution; a 1 indicates this is your least desired solution. Use the table to help you choose types of storage for your organization.

Table   19.1 Selected Hardware and Software Storage Solutions

Solution	Availability	Response Time	Capacity	Support for Multiple Users
CD-ROM/DVD-ROM	4 1	3	2-3	2
CD-ROM library	4	2	5	5
CD-ROM drive array	5	4	4	4
Dfs	5	3-4	5	5
Disk	3	4	3	3
Disk mirroring with two controllers (Duplex)	5	4	2-3	2
Disk stripe set	1	5	4	4
Disk stripe set with parity	4	3	3-4	4
Tape	3	2	4	1
Tape library	3	1	5	4
1 5 – High/1 – Low

After you have assembled a storage management team, identified your storage requirements, and determined your budget, you need to evaluate the storage capabilities of Windows 2000.