Wednesday, January 27, 2010

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The Myth of RAID Backups | RAID Is Not A Backup Function

RAID stands for Redundant Array of Inexpensive/Independent Disks. It's a set of hardware and/or software configuration(s) that grants you higher storage hardware availability (from failed disks), storage capacity, and/or gets you storage speed-nothing more. Some people are under the misconception that RAID can function as a backup for their system. This is simply not true.

RAID gets you hardware availability with respect to hardware failures (that is, it keeps things running after one of your hard drives die). Backups get you data availability with respect to time. RAID will NOT save your assets if you accidentally rm -rf /home (don't ever type that!), or if you accidentally rpm - Upgrade to the latest kernel instead of -installing it, nor will RAID help you get your data back if you get hacked, cracked, or rooted. When data is written to a RAID array, it gets written to ALL the disks. RAID will save you if one of your hard drives fails. That's all. Hardware availability with respect to, well, hardware!


Backups get you data availability for when your data fails (that is, rm - rf *, rpm - i kern*, or h4x0r3d). I've heard from many people who were baffled as to why they couldn't just recover their system from RAID. (These are likely the same unfortunate souls who thought that a firewall would protect them from the CodeRed or Nimda Internet Worms.) In short, if you want to protect your system from being down from blown drives, get RAID. If you want to protect your data and OS configuration from, well, yourself and others, get backups.


You may have heard of some newer forms of pseudo-RAID/backup-ish type technologies such as snapshots, LVM, and off line RAID-1 that do give some measure of "data availability" or backup type of functionality. But these are not very common, are beyond the scope of this chapter, and should not be confused with regular RAID-1 or RAID-5. Plus, these solutions do not get you all the security and flexibility of off-site rotated backup tapes.

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Haja Peer Mohamed H, Software Engineer by profession, Author, Founder and CEO of "bench3" you can connect with me on Twitter , Facebook and also onGoogle+

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