Zerto facilitates IT resiliency with a single VM replication platform

Zerto IT ResiliencyBack at Storage Field Day 16 in Boston, Zerto presented their VM replication software. It’s a block level, continuous hypervisor based replication, using a journal to log I/O in a VCR-like fashion. This enables you to rewind to any point in time that’s covered in the journal, and recover your VMs to that exact state. Zerto’s plans are a bit grander than “just VM Replication” though… they aim to cover the complete IT Resiliency market.

A-sync, near-zero, continuous data protection


Zerto Virtual Replication is deployed as an appliance: one vRA per hypervisor host. It supports a broad range of hypervisors and public clouds: VMware, HyperV, AWS, Azure and the IBM Cloud. One Zerto Virtual Manager (ZVM) per site manages these appliances on the hypervisor hosts.

Zerto Continuous Data Protection

You can manage the replication parameters by grouping virtual machines in Virtual Protection Groups. One of these parameters is the RPO, which can be configured as low as 1 minute. That’s a theoretical target though. When operational, Zerto will replicate data across as fast as it can. This could mean that the actual RPO is as low as 4-5 seconds.

After an initial synchronization, all new writes are transferred to the target site and stored in a journal. This is the only journal there is: there is no journal required on the source site. Zerto recommends this journal to be a high performance disk, preferably flash. The journal is attached to a vRA at the target site, and stores the writes in a proprietary format.

Zerto claims their continuous data protection has zero impact on the VM and hypervisor itself. VMotions, Storage VMotions and snapshots are still usable, and will not impact the replication nor the VM. There is some impact when reverting a snapshot, but that isn’t too much of a surprise. Zerto also supports virtual and physical RDMs for those pesky Microsoft Failover cluster environments, and doesn’t need any agents inside of the VMs.

But wait… that’s only one part of IT resiliency!

It’s all good to replicate your data to a different location for Disaster Recovery. But that’s only one component of IT resiliency. Two other components are backup and cloud mobility (or Hybrid Cloud, in Zerto’s marketing terminology).

Zerto IT Resiliency

Zerto isn’t the only player in this >$14 Billion market, and they want to conquer it with their experience in continuous protection, and the Elastic Journal.

Data is replicated to the DR site using their proven hypervisor based replication. The data is stored in the journal, and this composes their short-term retention. It ranges from a few seconds old, to a maximum of 30 days. The main use case for this short term retention is restoring files between 3 and 30 days old. In fact, this time span accounts for 86% of restores.

The long term retention is the second hop, and it’s stored in a classic backup target. Examples of targets include Exagrid, an NFS export or SMB share. Object store support is coming. The classic backup types such as dailies or weeklies are synthetics generated from this long term retention journal.

What this means is that you no longer need a backup window on your primary infrastructure. The backup is the second replication, and it’s coming from the DR site. This also means that backup will no longer impact the performance from your primary production site. And it’s all managed in a single product.

My thoughts on Zerto Virtual Replication and IT Resiliency

I have had some very bad experiences with hypervisor based replication tools from multiple vendors. There’s either a pile of snapshots that eat performance and space. Or the I/O filter isn’t located in a convenient location, causing all kinds of hiccups when you use other hypervisor features such as snapshots. Or it works well, but there’s only a fixed RPO and no continuous protection.

Zerto promises hypervisor replication that works. No snapshots, and a single IO filter agent in the ESX host. This replication would also be the stepping stone to a seamless long term retention or backup. A backup that moves the backup performance impact to the DR site, reducing impact on the primary site. This makes it ideal for demanding hypervisor environments, like a telco or ISP. I am looking forward to trying this out in real life soon! Check out the Zerto presentation for yourself over here.

Disclaimer: I wouldn’t have been able to attend Storage Field Day 16 without GestaltIT picking up the tab for the flights, hotel and various other expenses like food. I was however not compensated for my time and there is no requirement to blog or tweet about any of the presentations. Everything I post is of my own accord and because I like what I see and hear.