The debate over storage area networks vs. network attached storage, two phrases without a dime's worth of difference to most non-storage onlookers, is one about centralization vs. distribution.
The storage area network is a way of hooking up all the storage in a data center, or at least facilities located near each other, over a high speed, highly reliable, fiber-optic network. By doing so, the network administrator, database administrator or whoever is responsible for managing storage can double the amount of storage she can oversee.
"Studies have shown that one database administrator can handle about 350 gigabytes of direct attached storage (disk drive volumes directly attached to a server). With a SAN, that number can pop up to 700 or 800 GB," said Dick Blaschke, executive vice president of Xiotech, a supplier of a system that links diverse storage units together.
"Storage area networks are trying to hook up all the storage in the data center in a ring. Network attached storage is tied to a ring that already exists. It's called the worldwide Net (the Internet)," said Ali Jenab, senior vice president, Systems Division, of VA Linux Systems.
In his study, "Surviving the Storage Boom," Forrester Research storage analyst Carl Howe notes that many companies buy a new server and storage for each new application. "But rolling 100 copies of SAP, each on a different Windows NT server, just creates storage bloat," he said.
Instead firms should buy diskless servers and connect them to a SAN, so that each may draw on one pool of data, he wrote.
Such a move is also in step with the trend to consolidate servers into fewer and larger units. "Putting most of a company's NT and Unix productivity servers in one room makes SAN connectivity a snap," he noted.
But, he adds, it's not necessary to put data that is archived and used for data mining on the expensive SAN. "The firm doesn't need to guarantee 24 by 7 nonstop availability to the grocery store whose data shows that beer buyers also buy diapers," he said. That data should go on a $40,000 redundant array of independent disks from Compaq Computer and Dell Computer, he suggested. And those arrays might be network attached or direct attached storage, he said.