Why Zerto Performs a Delta Sync After Failover

This is an article about Zerto, the award-winning IT Resilience platform I was first exposed to in 2011 and loved so much that I joined the team in 2012. For help with any Zerto-specific terminology, see Zerto’s official product documentation.

Whenever you perform a Live Failover of any Virtual Protection Group (VPG) in Zerto you’re given the option to enable a feature called Reverse Protection. If enabled, the Reverse Protection feature automatically transposes the VPG configuration after recovery is complete so you don’t have to do it manually. The end result is a VPG configured to put things back where they came from.

One step in the Reverse Protection process that surprises some Zerto users is a Delta Sync. They ask what is Delta Syncing, why is a Delta Sync happening when Zerto should have the same data at each site, and more.

For more about the Zerto Delta Sync operation, see this post on the MyZerto forum.

Zerto performs a Delta Sync as part of Reverse Protection because Zerto inherently distrusts that VPG’s source-site data after a Live Failover event. We as people sometimes fall into the trap of assuming the source data must match the recovered data. After all, the application was shut down as part of the failover process, or the failover only took a minute or two! That assumption is incorrect for several reasons.

First, you are not failing over to the current application state because Zerto replicates asynchronously. The data may only be a few seconds old, but a few seconds is not zero seconds. Next, although you may elect to shut down the source application as part of the Live Failover, Zerto does not replicate data created by that application after you initiate the failover process. This is because, from a product design perspective, the Zerto software doesn’t fall into the “best case scenario” trap I mentioned earlier. Between the shutdown and the recovery, any one of dozens of events may have happened to alter the source application data, storage configuration, or the storage array itself. Zerto assumes a worst-case scenario, that the source and recovery site data may not be the same, and then validates this assumption using a Delta Sync.

If you do want a perfectly-synced application recovery, you want to use the Move operation instead of Live Failover. As with a Live Failover, the software assumes the worst and performs a Delta Sync (assuming you don’t disable Reverse Protection as part of the Move). Unlike a Live Failover, a Move will synchronize any data created by that application in the last moments before it is completely shut down and then “moved” to the recovery site.



The Trucking Industry is Doomed

I recently read an article about jobs that are disappearing in America. Trucking was listed as one of them. A commenter noted that there is unfilled demand for 50,000 trucking jobs. Amazing, right? Except they’re unfilled for a reason: although admittedly an anecdote, friends in the industry tell me that young people just aren’t going into trucking. It’s never been a glamorous job, but apparently now it’s not a high-paying or stable one either.

Rates have tanked. Trucking used to be a very lucrative career. Not so much now. Companies have figured out that it’s mostly about getting stuff from point A to B (I say this objectively, not making any claims about truckers whom I love!), and found as many ways as possible to reduce wages, hours, etc.

I’ll note that public data appears to contradict this, and I’m interested in any feedback if you’re in the industry and you’ve seen your pay rise or fall over the last couple of years. Leave a comment or contact me.

Trucking is also being fiercely automated. WalMart is pushing to automate and electrify it’s entire fleet by 2026 last I read. Tesla is betting on an automated future. Volvo, too. And Mercedes. Several other companies, such as Uber whose push toward automation threatens millions of another kind of transportation job, have jumped in as well.

Distribution and transportation jobs will first shrink to the local stage, where strange and ever-changing roads (at least in cities) confound drones and autopilot systems today. Then give it another few years and those will be gone as well. Drivers will just be attendants in the truck or car to fix anything that breaks, but they’ll be paid minimum wage because a computer will tell them exactly what is broken and how to fix it. No skill needed besides being human.

Don’t believe me? It’s not just private industry moving toward this future but the US government, from the White House through Congress, likely including your representatives, has been working behind the scenes to support the rise of the robots, largely without any plans regarding retraining or what happens next for all those displaced.

But that’s a post for another time.

What other careers and industries do you see being displaced by automation? Leave a comment or send me a note.

The #1 Thing Everyone Screws Up In Enterprise IT

Too many of us in Enterprise IT ignore this one critical thing about infrastructure management.


Users: we have huge egos. “My infrastructure is mine. I’ll do whatever I want with it. If your tech can’t keep up, too bad and screw you. I’ll buy something from someone else who “gets it”. I’ll post all over social media about how much you suck.”

Vendors: we’re slow and sniveling. “I can’t ever make demands of my customers. I can’t call them out when they mess up. They’re the smart ones. I’m just slinging tech. I’ll drop everything and get right on this.”



Unless you’re new to the field, you know better. The IT infrastructure is not your toy. Your title? Who cares. Are you the Founder? It’s still not yours, it belongs to the business. Period.


Unless not a single person on the team has ever done this, you know better. Your tech doesn’t exist in a vacuum. You’re a user of *something* and you know you ignore the warnings – you’re human! But you’re a vendor now and you need to know and act better.