Zerto vs ShadowProtect Comparison [2021]
By : Synextra

Zerto vs ShadowProtect in 2019

Data loss and downtime are two of the biggest threats facing IT managers on a daily basis. 75% of IT managers interviewed by ICAS said they weren’t able to restore everything when moving data, despite having a backup solution in place.

And in the same report, 22% of all enterprises that experienced a ransomware attack had to cease all operations to address the attack, with 1 in 6 ransomware attacks causing 25 hours or more of downtime.

Why? Because backups are only half of the puzzle.

IT Managers need more than just a solution that can safely and securely backup data with minimal impact on their network; they also need a solution that can help them restore that data as quickly and easily as possible in the event of a data loss incident.

In this article, we’ll compare Zerto vs ShadowProtect, two established providers in the DRaaS market that we have deployed and managed for customers at Synextra; Zerto Virtual Replication by Zerto and ShadowProtect SPX by StorageCraft.

About Zerto

Zerto is best known for pioneering the new method of data backups: journal-based recovery.

By using an ‘always-on’ approach to data replication, Zerto monitors block-level changes in ‘protected’ Virtual Machines with the Zerto journal, which essentially acts as a transaction log for all the changes made to a VM. All changes are tracked, no matter how large or small.

These changes are even tracked across multiple VMs that comprise a single application or application stack if necessary, to maintain application-consistent recovery.

This means that all of your critical files, folders, apps and VMs can be restored from any point in time, even just seconds before an incident, thanks to continuous data protection. Malware infection? Ransomware? Hardware failure? Human error? Any type of potentially business-ending fault can be recovered from in seconds, rather than in hours or even days.

Zerto-DR-Cloud-Overview This gif shows an overview of how Zerto operates within an enterprise server to replicate data live to the cloud.

About ShadowProtect SPX

ShadowProtect SPX is designed on an image-based backup and recovery model. You can backup and restore individual files and folders, or entire systems to the same physical or virtual environment.

ShadowProtect can also recover your systems to dissimilar hardware or a different hypervisor environment with its hardware-independent restore feature for Windows systems or its boot repair feature for Linux-based environments.

In order to accelerate the time taken to create backups images in Windows environments, ShadowProtect utilises the host operating system’s VSS writer to accurately calculate the changes between backup images.

With ShadowProtect’s ImageManager, you have the ability to cache images locally within your environment, verify and replicate them, as well as having the ability to ‘head-start’ restore them to a local hypervisor, which decreases RTO.

This gives you peace of mind that when you restore your environment, your snapshots have already been verified, so you won’t encounter any unexpected data errors.

ShadowProtect-SPX-functionality-overview This gif shows an overview of how ShadowProtect SPX operates within an enterprise server to backup data to the cloud.

Comparing ShadowProtect SPX to Zerto

There are some similarities between Zerto and ShadowProtect. Comparatively, both achieve the same goal, however, the technology used to achieve these goals are different.

Both work by tracking block-level changes. ShadowProtect monitors data at the sector level and only tracks the changed blocks in each sector. However, Zerto utilises a kernel integration to mirror read and write operations to the Zerto Journal.

So, whilst Zerto backup and replication is built from the ground up for enterprise hypervisors, ShadowProtect functions at a higher level in conjunction with the file system, as opposed to working with the hypervisor kernel.

“ShadowProtect is primarily a backup product with little focus on DR. The elements which make up the functionality for it to be a DR product were added later and are charged at an additional cost to end-users.

Meanwhile, Zerto was built from the ground up a DR product and did not originally have a long term backup feature. However, when it was added, Zerto spent considerable time on it to make it a true backup system replacement, hence why they call it the only IT Resilience Platform.”

Matthew Beckett, Infrastructure Engineer at Synextra.

Below are the fundamental differences between utilising Zerto and ShadowProtect in your DR strategy:

Features & Benefits:

Long-Term Retention

Both Zerto and ShadowProtect can facilitate long-term retention of data and can scale to protect years of changes.

DR Site Protection

With Zerto, read/write operations on the protected machines are sent to the DR site in real-time, meaning no backup replication time. However, with ShadowProtect, the options for remote protection are limited without the purchase of the additional ShadowStream license.


With ShadowProtect, your minimum RPO is 15 minutes with a variable RTO time, depending on if you are utilising the head-start restore function and how many backup images you have. Whereas with Zerto, the machines are always restoring to the destination site and the only time taken to restore a VM is the time taken to conduct the failover process.

With Zerto, your RTO could potentially be minutes, unlike ShadowProtect, which could take days.


Resource Overheads

ShadowProtect utilises an agent-based approach, which means that backups operate on a schedule. This can be very intensive if run infrequently on a production environment with a high rate of change.

With Zerto, there are no managed backup agents; all protection operations are conducted within the hypervisor. This results in a minimal performance impact as all changes are sent to the DR site in real-time, with no schedules or intensive backup jobs slowing down your applications.


Zerto offers real-time RPO/RTO statistics and can send alerts to your staff if they are not being met, whether due to a performance or connectivity issue.

Zerto also offers a mobile application to give you real-time visibility over your protection groups, even if you are working remotely.

StorageCraft offers a virtual appliance called ShadowControl, that allows for the central management and monitoring of ShadowProtect instances. This system can also send automated emails to staff when backups fail.


RTO Optimisation

Whilst Zerto is always working in the same way as ShadowProtect’s ‘head-start restore’ functionality by replicating to the target environment around the clock, ShadowProtect requires you to manually configure this feature.

Known as ‘lag-time’, you must configure how many hours behind real-time you wish the head-start restored virtual machines to exist. In the event of a disaster, you are able to select any point in time between the lag time and the current time.

If you choose a shorter lag-time to decrease your RTO and a disaster goes unnoticed, there’s a risk that damaged blocks can be rolled into the head start restore. In the event of this, the whole machine will have to be restored again, which for large machines can increase RTO by days.

However, a longer lag time can also equal a potentially higher RTO too.

Ease of Use

If you are not utilising head-start restore, restoring in ShadowProtect requires you to boot into a recovery environment based on WinPE and connecting it to the backup repository manually. Zerto, on the other hand, will do the entire restore process for you automatically.


Zerto can only integrate with hypervisors connected to a VMWare vCenter or Microsoft System Center Virtual Machine Manager.

However, you can install ShadowProtect on any laptop, desktop or server you wish to protect. This greater versatility means you can protect and restore devices regardless of the environment or technology stack.

Zerto vs ShadowProtect summary Zerto Wins Race


As with everything in IT, no two environments are the same. Every organisation has differing requirements and no one solution can be all things to all IT managers.

Our Cloud Solution Engineers have used both ShadowProtect SPX and Zerto, and we have now standardised with Zerto Backup for all new customers thanks to its ease of use, impressive feature set and reliability.

Hopefully, this breakdown will showcase the pros and cons of Zerto vs ShadowProtect, allowing you to make an informed decision about your new DR solution.

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