Over the past few years, Changed Block Tracking (CBT) has drastically transformed backup operations on virtualization platforms. Thanks to CBT, now VM backup vendors can perform incremental backups by tracking blocks within virtual machine storage as they change in time. That means backup cycles are now smaller, faster, and more efficient. Some notable VMs that offer CBT include VMware, Microsoft Hyper-V, and Citrix XenServer.
In this article, we’ll focus on the functionality that exists in the Hyper-V and VMware CBT technologies, and their key differences.
What is VMware Changed Block Tracking?
CBT technology is a VMKernel storage stack that tracks changes in log files on a virtual machine at specific points in time. It was first introduced in VMware vSphere 4.0. This feature seeks to optimize backups by identifying only the altered disk sectors from a previous backup rather than all blocks in the VM infrastructure. It can also track blocks that are in use on the Virtual Machine File System (VMFS) partitions. For an efficient backup, VMware vSphere Storage APIs – Data Protection works with third-party VM backup solutions to back up the virtual machine from an off-host LAN-free server without shifting this task to ESX/ESXi hosts.
What is Resilient Change Tracking (RCT)?
Changed block tracking is a relatively recent technology in Hyper-V virtual machines. Before 2016, Hyper-V had no native CBT. Instead, backup vendors scaled through this process by creating filter devices to track these changes. With the introduction of the Windows Server 2016 came a built-in system of resilient change tracking. Similar to VMware CBT, RCT enhances incremental backups, making it easier and faster.
VMware CBT vs Resilient Change Tracking
On a broader scale, these two features are similar. They allow incremental backups of virtual machines and can be accessed by third-party VM backup software. However, there are some differences in their functionality which we have highlighted below.
| Resilient Change Tracking | VMware CBT | |
| Storage Deployment | Its native Resilient File System (ReFS) clustering capabilities are complex. | The Clustered Shared Volume (CSV) functionality in its VMFS has more flexibility. |
| Snapshot Technology | Allows 64 checkpoints per VM | Allows 32 snapshots per VM |
| Checkpoints are persistent | Snapshots are transient | |
| Can run in production | Does not recommend this functionality | |
| Support | Requires Microsoft Windows Server 2016 or newer versions | Requires at least v4.0 ESXi host |
| Available on Hyper-V VM v6.2 or later | Available on VM hardware v7 or later |
Which is Better: Changed Block Tracking or Resilient Change Tracking?
These two solutions are the most common CBT technologies in VM backup. Backup vendors can use any of them to perform full and incremental backups efficiently. However, choosing between both would require you to look beyond the change block tracking functionality to the overall benefits Hyper-V or VMware platforms offer to your organization.
NAKIVO Backup 7 Replication allows you to create seamless incremental backups in VMware and Hyper-V environments. Download a full-fledged free trial today to test if our solution is right for your business.
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Changed Block Tracking vs Resilient Change Tracking: Key Differences
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Are you looking to perform incremental backups in your organization’s VM platform? Read on to learn the ideal solution between VMware CBT and Resilient Change Tracking.
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