Storage Management Strategies for the CIO
What you will learn from this tip: How RAID 50 combines striping with distributed parity for higher reliability and data transfer capabilities.
Like the other double-digit RAID levels, RAID
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50 is a combination of two basic RAID techniques. It combines striping (RAID 0) with
independent data disks with distributed parity (RAID 5). It stripes data across at least two RAID 5
arrays.
The easy way to think of RAID 50 is as RAID 5 with an extra pair of suspenders. RAID 50 offers increased write performance and better data protection, including faster rebuilds, than RAID 5 in the event of a disk failure. While performance degrades in the event of a disk failure, it doesn't degrade as much as it would in a RAID 5 array because a single failure only affects one of the arrays, leaving the other fully functional. In fact, RAID 50 can sustain up to four drive failures if each failed disk is in a different RAID 5 array.
RAID 50 is best used for applications that need high reliability, and that need to handle high request rates and high data transfer with lower cost of disks than a RAID-10 (striped and mirrored) array. However it takes a minimum of six disks to set up a RAID 50 array.
One of the disadvantages of RAID 50 is that, like RAID 5, it needs a sophisticated controller. For maximum throughput, a RAID 50 array should have synchronized disks, which limits disk choices since not all disks can be synchronized.
For more information:
Tip: RAID-10 -- Two great RAIDs that go great together
Tip: How to choose the right RAID for your array
Tip: A quick and dirty way to increase a RAID-5 array
About the author: Rick Cook has been writing about mass storage since the days when the term
meant an 80 K floppy disk. The computers he learned on used ferrite cores and magnetic drums. For
the last 20 years, he has been a freelance writer specializing in storage and other computer
issues.
This was first published in March 2005
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