It was at VMware Explore Europe 2022 when I ran into a colleague from Dell who told me about “transparent snapshots” and mentioned that their solution has something in common VMware Cloud Disaster Recovery (VCDR). After doing some research, I figured out that he was talking about the Light Weight Delta (LWD) protocol.
Snapshots
Snapshots are states of a system or virtual machine (VM) at a particular point in time and should not be considered a backup. The data of a snapshot include all files that form a virtual machine – this includes disks, memory, and other devices like network interface cards (vNIC). To create or delete a snapshot of a VM, the VM needs to be “stunned” (quiesce I/Os).
I would say it is common knowledge that a higher number of snapshots negatively impact the I/O performance of a virtual machine. Creating snapshots results in the creation of a snapshot hierarchy with parent-to-child relationships. Every snapshot creates a delta .vmdk file and redirects all inputs/writes to this delta disk file.
VMware vSphere Storage APIs for Data Protection
Currently, a lot of backup solutions use “VMware vSphere Storage APIs for Data Protection” (VADP), which has been introduced in vSphere 4.0 released in 2009. A backup product using VADP can backup VMs from a central backup server or virtual machine without requiring any backup agents. Meaning, backup solutions using VADP create snapshots that are used to create backups based on the changed blocks of a disk (Changed Block Tracking aka CBT). These changes or this delta is then written to a secondary site or storage and the snapshot is removed after.
Deleting a snapshot consolidates the changes between snapshots and previous disk states. Then it writes all the data from the delta disk that contains the information about the deleted snapshot to the parent disk. When you delete the base parent snapshot, all changes merge with the base virtual machine disk.
To delete a snapshot, a large amount of information must be read and written to a disk. This process can reduce the virtual machine performance until the consolidation is complete.
VMware Cloud Disaster Recovery (VCDR)
In 2020, VMware announced the general availability of VMware Cloud Disaster Recovery based on technology from their Datrium acquisition. This new solution extended the current VMware disaster recovery (DR) solutions like VMware Site Recovery, Site Recovery Manager, and Cloud Provider DR solutions.
VMware Cloud Disaster Recovery is a VMware-delivered disaster recovery as a service (DRaaS) offering that protects on-premises vSphere and VMware Cloud on AWS workloads to VMware Cloud on AWS from both disasters and ransomware attacks. It efficiently replicates VMs to a Scale-out Cloud File System (SCFS) that can store hundreds of recovery points with recovery point objectives (RPOs) as low as 30 minutes. This enables recovery for a wide variety of disasters including ransomware. Virtual machines are recovered to a software-defined data center (SDDC) running in VMware Cloud on AWS. VMware Cloud Disaster Recovery also offers fail-back capabilities to bring your workloads back to their original location after the disaster is remediated.
Note: Currently, VCDR is only available as an add-on feature to VMware Cloud on AWS. The support for Azure VMware Solution is expected to come next.
To me, VCDR is one of the best solutions from the whole VMware portfolio.
High-Frequency Snapshots (HFS)
One of the differentiators and game-changers are these so-called high-frequency snapshots, which are based on the Light Weight Delta (LWD) technology that VMware developed. Using HFS allows customers to schedule recurring snapshots for every 30 minutes, meaning, that customers can get an Recovery Point Objective (RPO) of 30min!
To enable and use high-frequency snapshots, your environment must be running on vSphere 7.0 U3 or higher.
With HFS and LWD, there is no Changed Block Tracking (CBT), no VADP, and no VM stun. This results in better performance when maintaining these deltas.
Transparent Snapshots by Dell EMC PowerProtect Data Manager (PPDM)
At VMworld 2021, Dell Technologies presented a session called “Protect Your Virtual Infrastructure with Drastically Less Disruption [SEC2764S]” which was about “transparent snapshots” – image backups with near-zero impact on virtual machines, without the need to pause the VM during the backup process. No more backup proxies, no more agents.
As with HFS and VCDR, your environment needs to run on vSphere 7.0 U3 and higher.
How does it work?
PowerProtect Data Manager transparent snapshots use the vSphere API for I/O (VAI/O) Filtering framework. The transparent snapshots data mover (TSDM) is deployed in the VMware ESXi infrastructure through a PowerProtect Data Manager VIB. This deployment creates consistent VM backup copies and writes the copies to the protection storage (PowerProtect appliance).
After, this VIB (Data Protection Daemon (DPD) which is part of the VMware ESXi >7.0 U3 image has been installed on the ESXi host) tracks the delta changes in memory and then transfers the delta changes directly to the protection storage.
Note: PPDM also provides image backup and restore support for VMware Cloud on AWS and Azure VMware Solution, but requires VADP.
Light Weight Delta (LWD)
It seems that LWD has been developed by VMware but there is no publicly available information out there yet. I only found this screenshot as part of this Dell article:
It also seems that Dell is/was the first who could leverage the LWD protocol exclusively but I am sure it will be made available to other VMware partners as well.
