What Is a Non-Disruptive Upgrade (NDU)?

What Is a Non-Disruptive Upgrade?

A non-disruptive upgrade (NDU) is a software upgrade, hardware expansion, and/or replacement that doesn’t impact data availability or performance. In an ideal scenario, that means no downtime, no data migrations, and no degradations in performance.

In practice, you’re more likely to encounter an NDU in degrees. Most all-flash storage solutions support some form of a non-disruptive upgrade today. Some require proactive planning or days of background data migration, while others can scale only as long as the hardware is identical, locking customers in to quickly outdated hardware models.

Pure Storage® all-flash arrays not only match the resiliency of legacy Tier 1 arrays, but they also raise the bar with 100% performance availability during maintenance operations: Software upgrades, capacity expansion, and controller upgrades (including next-gen controller upgrades) are all performed non-disruptively. No downtime or data migration required.

How to Perform Non-Disruptive Upgrades

The general approach to NDUs is to migrate data to a takeover system while the storage system is being upgraded. The takeover system assumes all operational responsibilities of the storage system until the upgrade is completed, and data can be migrated back to the upgraded system. While this may sound simple enough, migrating live, constantly-changing data that’s powering software solutions actively being used by your customers is no small feat. It requires a lot of coordination and planning to perform these migration services without causing an impact to your business. 

Here are a few key questions to consider before performing a traditional NDU:

• Do you have enough power and space in the data center to accommodate the new hardware?
• Do you have the additional Ethernet and Fibre Channel ports available to connect the new array hardware?
• How do you plan to handle routing and network configuration of the new hardware as you swap out older storage units?
• Which migration tool will you be using, and will a host reboot be required?

At the end of the day, performing an NDU is a tricky process where you must ensure compatibility between all the different hardware and software layers. And we haven’t even touched on the planning and labor needed to unzone, uncable, and unrack the old array. With all these factors, it’s not surprising that most vendors settle for something just short of ideal depending on the unique needs of their customers.

Why Choose Pure for Non-Disruptive Upgrades?

Pure is the first vendor to design an all-flash storage array to achieve truly non-disruptive upgrades that maintain availability without data migrations or degradations in performance. 

The concept of an NDU is baked into the architecture of FlashArray™ itself, including:

• A stateless controller that decouples data integrity from the physical hardware;
• Host I/O write data that is stored on the RAM devices instead of the controller, allowing you to swap controllers without data migrations; and
• Purity Operating Environment software, which handles dynamic controller failovers (i.e., the handover of I/O responsibility to a takeover system), ensuring full controller transparency.

The end result is a system that allows non-disruptive upgrades. As a result, your infrastructure stays modern and agile without any disruptions to critical applications or your business.