Test your SAN aggressively
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Bill Peldzus, storage consulting marketing manager at Imation's Storage Professional Services Group has a piece of advice for anyone installing a SAN: Test the heck out of it.
"Our take is that you need to test it aggressively with the mindset to break it," Peldzus says.
One of the problems with SAN installations, Peldzus says, is that companies installing them don't push them hard enough in testing. They quit testing when everything seems to work right without considering the effects of heavier loads, adding more servers and other real-world conditions. As a result they are setting themselves up for failure. "It's better to break a SAN in a pristine lab than to have it up and running for a couple of weeks and then it's dropping left and right because you added twelve more servers to the application," Peldzus says.
"You want a SAN that's stable from a load, saturation and repeatability standpoint," Peldzus says. The only way to make sure you've achieved that is to test your SAN to its limits so you know what those limits are. Many times potential problems can be avoided if you know in advance that, for example, your SAN configuration will only support so many LUNs, or so many mappings. If you know you can work around the problems.
Finally, Peldzus suggests testing repeatedly to make sure you've uncovered all the gotchas. "If it works ten times don't assume it will work the next time," he says. "Try it 1,000 times."
There are a number of ways to test your SAN, some of which would require you to do the programming, some of which are packages from vendors. A simple test is Intel's freeware Iometer program. You can use Iometer to assign devices in a SAN to the computer running the test and exercise the SAN in that fashion. Be sure to read all the disclaimers on the site before you download and use Iometer.
Also, Shugart Technology has some new software that purports to enable testing of fibre-optic based SANs.
Rick Cook has been writing about mass storage since the days when the term meant an 80K floppy disk. The computers he learned on used ferrite cores and magnetic drums. For the last twenty years he has been a freelance writer specializing in storage and other computer issues.
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Storage Area Networks: Designing and Implementing a Mass Storage System, 1/e
Author : Ralph Thornburgh and Barry Schoenborn
Publisher : Prentice Hall
Published : Sep 2000
Every month, enterprises require more information, delivered faster, with greater reliability -- and traditional data storage methods no longer suffice. Enter the Storage Area Network (SAN), which can store enormous amounts of data, serve it at lightning speed, scale to meet accelerating growth, and deliver unprecedented reliability. Now, there's a complete guide to SAN technology for every IT professional and decision-maker. Storage Area Networks covers it all: key concepts, components, applications, implementation examples, management, and much more.