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April 2024: What's New?

· 4 min read

April 2024: What's New?

Written by Callum Sinclair - Product Engineering Manager

What's New? is a series of blog posts covering recent changes to Comet in more detail. This article covers the latest changes in Comet over April 2024.

There were three Comet releases during April - two in the Voyager release series, plus one update for our Mimas release series.

We've landed a few large and exciting features this April:

Hyper-V CBT (Changed Block Tracking)

Hyper-V CBT is now available in our Voyager series. Hyper-V CBT performs efficient backups of Hyper-V Virtual Machines by only reading blocks of a virtual disk that have changed since the last backup job. This means Comet only needs to upload the data that has changed inside the VM without having to read and upload every byte.

You will find two new Hyper-V Backup Mode types when setting up a Hyper-V Protected Item. These are Latest VM State (Changed Block Tracking) and Latest VM State (Standard). You can read more about what these new modes do in our documentation here

Under the hood our two new Hyper-V Backup Mode types use WMI (Windows Management Instrumentation) and RCT (Windows Resilient Change Tracking) to perform the backup. This is a completely new way for Comet to backup Hyper-V VMs as our old implementation used Windows VSS (Windows Volume Shadow Copy Service).

New Hyper-V Backup Option One: Changed Block Tracking using WMI and RCT

New Hyper-V Backup Option One: Hyper-V Backup using WMI

Hyper-V Changed Block Tracking Using

This enhancement improves our Hyper-V backup offering, ensuring faster backups of your Virtual Machines while also needing to upload less data.

Impossible Cloud Storage Templates

We're pleased to announce that Impossible Cloud is now available as a built-in Storage Template in our Voyager series. If you enter top-level credentials into the Storage Template, Comet can use them to provision private buckets with separate credentials for each user, allowing seamless direct-to-cloud backup.

Impossible Cloud IAM Storage Template

Impossible Cloud IAM Storage Template with Object Lock

Impossible Cloud Partner API Storage Template

As a quick reminder - when using the Storage Templates, it's likely you'll want to configure cleanup for cloud buckets that are no longer being used by any user account. Comet's solution for this problem is called Constellation Role, and it's available from the settings page of your Comet Server. In Constellation, you can enter the same credentials for it to search through. When a Constellation report runs, it finds all your buckets; checks all the user accounts; cross-references the users' Storage Vaults with the available buckets; and deletes any discovered buckets that are not in use by any user account.

Constellation Role is designed to scale up to clusters of multiple Comet Servers, with any mix of server replication, Storage Role, or direct-to-cloud buckets created by the Storage Template feature. You should have exactly one Constellation Role server amongst your entire cluster of Comet Servers.

Comet-Hosted Single Sign On

Users can now sign into Comet-Hosted servers using their accounts. This feature simplifies access to Comet-Hosted servers, allowing users to utilize their existing Comet Backup account credentials for authentication. To enhance security, users are encouraged to set up two-factor authentication (2FA) on

This feature has already been enabled, and will be used the next time you click the login button from the My Services page on

In addition, once you have clicked the login button on the My Services page you will notice the new "Login with Comet Account Portal" button appear on the login screen of your Comet-Hosted server. This button will only appear on browsers where you have clicked the My Services login button before. We have done this to ensure we don't break any rebranding you have configured by showing a big "Login with Comet Account Portal" button.

Comet-Hosted London Region Now Available

We are pleased to announce that Comet-Hosted is now available to be hosted in the London region. Comet users now have the choice of four geographically diverse locations to choose from when selecting where their Comet-Hosted server should be located.

Continued Comet Improvements

Throughout April, we rolled out over twenty fixes and enhancements aimed at improving the overall quality and performance of Comet. These updates underline our commitment to providing a reliable and efficient backup solution for our users.