The Storage Rack: The Impending RAID Crisis

By Mike New

May 15, 2008 —  (Page 1 of 3)

RAID has gotten to be a bit too big for its britches.

I first started doing time in data centers in the 1980s, a period when disks were huge but didn’t hold much data, when an IT manager knew what “sense switches” were, when computers ran on coal, and when some companies actually made a business out of vacuuming out disk packs. My younger readers have no idea what I am talking about.

Storage was different then. Disks were small in capacity but large in footprint; a 180MB device, for example, took up a full three “U’s” on a 19-inch rack. And while disks were faster than tape and more reliable, they were not nearly reliable enough. So a group of academics came up with RAID, a mechanism for coping with the fact that all disks, eventually, would fail. RAID aggregated a number of disks into a single logical entity that offered either increased read performance, improved reliability, or both. It turned out this, like digital watches, was a pretty good idea, and RAID in its various incarnations has been with us ever since.

RAID comes at a cost, of course. In addition to paying for racks, bays, controllers and such, budgets also have to accommodate the fact that RAID devices always hold significantly less data than do JBODS. With RAID 5, for example, a useful rule of thumb is to subtract about 20 percent of raw disk space for the parity stripe. If your sales guy has convinced you that you need RAID 6, subtract another 20 percent for an additional stripe and try to ignore the fact that you will now have to buy (and provide power to) 40 percent more disks than you had originally planned on. Never mind that, though, as I’m sure you have no budget or energy cost issues at your data center.

Right.

In fact, it turns out that while the costs associated with RAID may be painful, they are also costs most IT managers are willing to bear to protect valuable data.

Related Search Term(s): Data centers, storage hardware, storage management

Share this link: http://www.sysmannews.com/link/32197