Systems Engineering and RDBMS

What RAID is Best for You?

Posted by decipherinfosys on January 30, 2007

Most of you are familiar with the basic RAID technologies avaible out there today, but it is always good to have too much information about this topic than not enough. Here is a brief yet informative summary of the most popular hardware RAID configurations, including pros and cons for each:

RAID-0 (Striped)

  • Does not provide fault tolerance
  • Minimum number of disks required = 2
  • Usable storage capacity = 100%
  • This is the fastest of the RAID configurations from a read-write standpoint
  • Is the least expensive RAID solution because there is no duplicate data
  • Recommended use for temporary data only

RAID-1 (Mirrored)

  • Fault tolerant – you can lose multiple disks as long as a mirrored pair is not lost
  • Minimum number of disks required = 2
  • Usable storage capacity = 50%
  • Good read performance, relatively slow write performance
  • Recommended for operating system log files

RAID-5 (Striped with Parity)

  • Fault tolerant – can afford to lose one disk only
  • Minimum number of disks required = 3
  • Usable storage capacity = subtract 1 whole disk from the total number in the array (i.e. 3 60Gig hard drives would provide 120Gig of usable disk space)
  • Generally good performance, and increases with concurrency – the more drives in the array the faster the performance
  • Recommended for operating system files, shared data, and application files

RAID-0+1 (Striped with Mirrors)

  • Fault tolerant – you can lose multiple disks as long as both are not part of a mirrored pair
  • Minimum number of disks required = 4
  • Usable storage capacity = 50%
  • Generally good performance, and increases with concurrency – the more drives in the array the faster the performance
  • Recommended for operating systems, shared data, application files, and log files

Additional Things to Keep in Mind

  • If you are using more than two disks, RAID 0+1 is a better solution than RAID 1
  • Usable storage capacity increases as the amount of disks increases, but so does the cost of the configuration
  • Performance increases as you add disks, but again, so does cost

7 Responses to “What RAID is Best for You?”

  1. […] 2008 We have covered RAID levels before in our posts. You can read about the different RAID levels here and the I/O characteristics here.  While building up a DR (Disaster Recovery) environment for one […]

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