Build Your Own RAID Storage Server with Linux - Page 2

By Carla Schroder | Feb 19, 2008
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Software RAID vs. Hardware RAID Smackdown

Ever since the vi vs. Emacs wars died of boredom it's been difficult to find good flamefests. Even software RAID vs. hardware RAID has become mundane. But it's worth reviewing the merits of each, because this isn't a case of one being clearly superior over the other, but deciding which one meets your needs best.

I wouldn't even bother with a PATA RAID controller; they're more trouble than help. SATA is where it's at these days. First the advantages of a good-quality SATA hardware controller:

  • Offloads all the processing from the CPU
  • Add more disks than your motherboard allows
  • No booting drama

The two disadvantages of good RAID controllers are cost and inflexibility. 3Ware controllers are first-rate, but not cheap. Hardware controllers are picky about what hard disks you can use, and the entire disk must belong to the array, unlike Linux software RAID which lets you select individual disk partitions. Recovery from a controller failure means you need the exactly correct new controller. Some admins think that using a hardware controller is riskier because it adds a point of failure.

Poor-quality hardware RAID controllers are legion. Those onboard RAID controllers and low-end PCI controllers aren't really hardware controllers at all; they do all their work in (usually crappy) software.

Linux software RAID has these advantages:

  • Cost- free!- and these days CPU cycles cost a lot less than good hardware RAID controllers
  • Very flexible; mix-and-match PATA and SATA, individual partitions
  • More recovery options: any Linux PC can rebuild an array

If I were running a super-important mission-critical server that had to be up all the time and no excuses, I'd use SCSI drives and controllers. For everything else, Linux RAID + SATA + LVM. Why do we want LVM? So we can resize our storage volumes painlessly. Come back next week to commence construction.

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