Large-Scale Data Backups with RAID 5

Posted on January 23 2017

Recently, we looked at RAID 1 (mirrored) backups with two hard drives for extra data protection. If you missed that post, you can read it here. But what happens if you need extra data protection and more than the few terabytes of space provided by a two-drive solution?

If you require upwards of 4TB of RAID-protected storage capacity, then RAID 1 just won’t cut it. And that’s where RAID 5 steps in.

Along with RAID 1, RAID 5 is one of the most popular and widely used of the many different RAID configurations. RAID 5 involves data spread across three or more disks, meaning more storage space, with the same ability to keep your data intact if a drive happens to fail.


How RAID 5 works:

When data is written to a RAID 5 array, blocks of data are striped across all drives in the RAID interspersed with what is known as a “parity block.” These parity blocks are distributed in such a way that they are on a different drive in the array for each data stripe. This is why it doesn’t matter which drive fails in the RAID 5 array – the data on the failed drive can be rebuilt with the help of the parity data on the remaining drives in the array.


This is how data is written to a RAID 5 array with "distributed parity."
A RAID 5 array with distributed parity blocks.

Benefits of RAID 5 Backups:

  • Easy to setup and use – simple backups for home and business environments
  • Massive storage capacity as compared to RAID 1 for the same number of redundant disks (1)
  • The RAID array is not destroyed by a single drive failure
  • Data Read speeds are very fast


Risks & Disadvantages of RAID 5:

  • Slower Write performance due to the extra “parity block”
  • When a drive fails, the RAID is operating in an unprotected mode and a second drive failure can result in total loss of data (RAID 6 can overcome this)


So what is RAID 6?

RAID 6 is an extension of RAID 5 that uses two distributed parity blocks instead of one, as described above. We will explore RAID 6 in depth, including a comparison with RAID 5 in a future post, so please stay tuned.

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