Active-Passive vs Active-Active Storage Controllers: What you should know before you buy one

Active-Passive vs Active-Active Storage Controllers

There’s a lot of misconception among IT professionals about the difference between Active-Passive storage controllers and Active-Active Storage controllers. Most believe that the Active-Active storage controllers are superior because they work in unison and are lower priced whereas others prefer active-passive storage controllers for constancy over speed.

Which storage controller should you buy? Active-passive or Active-active.

Let’s start from the beginning i.e. what is the purpose of a storage controller in a data center?

Storage 101:

Storage controllers, according to Storage Switzerland, are responsible for running the storage arrays. This means if a storage controller fails, the storage array will go offline and the storage and retrieval process will halt.

Therefore, keeping redundant storage controllers is eminent for the flawless working of the servers.

You can read the full post on what storage controllers actually do in our previous blog. However, if you do not have time for that, read this overview.

Storage controller is actually an x86 processor that:

  • Receives read & write requests from host (Fibre Channel or iSCSI channel)
  • It then processes data i.e. de-duplication, compression, metadata handling, cloning including some other features.
  • And finally, it writes/reads to/from the disk.

Now coming back to the topic of what actually is the difference between Active-Active & Active-Passive Controllers.


In Active-Active storage controller mode, both the controllers support Logical Unit Numbers (LUNs) and their volumes. In the case of the failure of one storage controller, the other continues to work. Therefore, the performance is downgraded but, on the upside, the process continues flawlessly.


  • Active-Active controllers are low in cost.
  • Data center professionals love them because of their higher performance levels.
  • Storage controller failure is rare so most will not spend more on buying an expensive storage controller when a lower priced one can do the same work.


  • Performance will drop if one storage controller fails


In Active-Passive storage controller mode, a single storage controller is working at a time, the second controller only takes its place if the first storage controller fails.


  • Both controllers in Active-Passive Storage controllers provide the same speed, hence they are more expensive.
  • There is no drop in performance in the case of a storage controller failure.


  • The passive storage controller remains idle for most of its life as the failure of storage controller occurs rarely.

Which Storage Controller is Better for You?

A vast majority of the IT professionals choose active-active storage controller design because it provides an adequate level of performance at the minimum price. They are ready to risk a future performance drop for a high-performance level at this time – which is fairly reasonable as storage controller failure is a rare occurrence overall.

However, there are organizations that utilize Active-Passive controllers because of their durability. Organizations that can compromise on performance but require stable systems, such as governments, libraries, social networks and others, usually use the latter.

If you have any questions about storage controllers or you would like to know where you can buy one, kindly message us on Or, contact us at our toll-free number 1-800-821-3354.

Have we missed something? Let us know in the comments section below.

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