Network Storage Tips

RAID6 Dual Redundancy – A Big Improvement Over Hot Spares

Hot Spares R.I.P.

I am really excited about RAID6 dual redundancy which is available on many NAS devices of 4 drives or more, although with Netgear ReadyNAS they do not give you the option unless the device’s total capacity is 6 drives or more. (Don’t ask me, Netgear does not have me on the payroll).

There are many import things to remember about RAID NAS.

  1. All hard drives will fail eventually.
  2. When a RAID array loses a hard drive, losing one more hard drive equals data loss in the most typical scenarios.
  3. There is no law that says two hard drives cannot fail the same day. In fact, Murphy’s law says they can and I just had both headlights in my car burn out the same day. With electronics anything is possible.
  4. Even if you have a hot spare configured for your RAID array, the array is vulnerable until that hot spare is fully synchronized.
  5. With today’s massive hard drives, synchronizing that hot spare – especially while users or applications are accessing the array – can easily take all day.
  6. Unless you have some way of being notified when a drive fails so that you can take immediate action, drives can continue to fail unnoticed until you suffer data loss and your array goes offline. All NAS devices reviewed on this site have the ability to configure email notifications and usually are supplemented by drive indicator lights on the front as well.

Enter RAID6 Dual Redundancy

With RAID6 dual redundancy, it is like having a hot spare that is continually synchronized. Therefore, losing two hard drives in quick succession leaves your array vulnerable to data loss should a THIRD drive fail, but keeps data integrity and availability while you scramble to get replacement drives acquired and installed.

You should waste no time in doing so.

Yes, it can take longer to get those replacements if you are in a warranty situation and wish to receive the replacement drive(s) at no cost. That is one advantage to the enterprise drives from Seagate that are included in Netgear ReadyNAS units (business lineup only-and NV+, 1TB and larger). The last time I checked they had an express replacement program.

Prosumer Ultra 6 Offers RAID6

netgear readynas ultra 6It is not often that consumers can get a feature like RAID6 with dual redundancy without spending an absolute fortune on a business class unit. While not available on the new prosumer Ultra 4, the ReadyNAS Ultra 6 does offer the configuration option of RAID 6 dual redundancy as long as you have at least four hard drives in the system.

This is an important feature in my book.

Look at that list above again, and wander toward the bottom. You need to be notified when a drive dies and take prompt action to ensure RAID array integrity.

Most consumers will buy a device like this and use the phrase I have heard until I puke:

“why would a drive die, it’s not that old?”.

Again, it’s electronics, and like a light bulb can last one day or one hundred thousand days. Not to mention environmental factors like placing the desktop NAS on a desk – huh, that seems logical, but then banging the drawers on the desk which is NOT good for hard drives!

So buying a Netgear ReadyNAS Ultra 6, then configuring with at least four drives – note that they currently come preconfigured with zero or three drives – grants you the protection and piece of mind of RAID6 with dual redundancy.

The question is: “how much do you value your data?”


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