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November 2023: What's New?

· 6 min read

"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 Voyager over November 2023.

There were seven Comet software releases during November - four in our 23.9.x Voyager release series, two point releases for our 23.8.x Adrastea quarterly series, and the official launch of our latest 23.11.0 Saturn quarterly release.

VMware ESXi Free edition support

Last month, we launched our newest Protected Item type to add support for backing up VMware virtual machines using Comet. Over the last month of Voyager series releases, we've seen great uptake of the new feature and have been working to improve it based on your feedback, including improved performance, compatibility, and correctness.

The VMware vSphere hypervisor platform encompasses both the ESXi hypervisor as well as the vCenter centralized management application. ESXi is available in multiple licensed editions, including a free license with various limitations such as restrictions on the number of virtual CPUs that can be assigned to a given virtual machine.

In our first release, Comet supported ESXi versions with a paid license ("vSphere Essentials" or higher), but in the latest Comet 23.9.11 we took a closer look at the problem, and have extended our compatibility to include support for the free version of VMware ESXi. Our implementation supports the same versions (6.7, 7.x, 8.x) of ESXi and is built solely using VMware's officially supported vSphere VADP backup APIs, including Changed Block Tracking (CBT) support. No configuration changes are required to your free-license ESXi host server to support this backup mode.

Improved restores

As part of working on virtual machine features this month, we put a particular focus on the granular restore option. The existing granular restore mode in Comet allows you to take a virtual disk backup at the block level - either of VMware, Hyper-V, or of a physical Disk Image - and then restore individual files and folders from the interior NTFS filesystem.

Our granular restore feature gives competitive restore performance and offers flexible interactive browsing, all while supporting multiple disk image and partition formats, using Comet's encrypted deduplicated cloud storage.

This month, we've made granular restore even faster and have reduced its memory and network traffic requirements, by using an intelligent caching system that helps Comet traverse the virtual NTFS file table in a more efficient way. We have streamlined the restore and browsing workflows to reduce edge cases, improving support for virtual machines with multiple disks, disk images in subdirectories, disk images that span multiple files, and other such cases. In addition, Comet is now able to display each partition's name in more cases.

Outside of granular restore, we've also optimized our ordinary file restore further by removing bottlenecks that could stop Comet from effectively multithreading. In the latest versions of Comet, it should be much faster to restore very deep directory trees.

Comet Server security and policies

Comet Server has an extensive permission system for administrators, tenant administrators, and end users. Comet recently added support to allow a top-level administrator to restrict a tenant administrator into using certain policies. However, as this restriction was not transitive, the tenant administrator could still allow a tenant end-user to bypass those policy restrictions. The latest version of Comet adds a new ability to enforce settings and preferences across an entire Comet Server.

Without careful consideration, adding features can sometimes result in a cluttered user interface. As Comet Server has grown to offer more and more control over user permission levels, we have split out the administrator permission settings onto a separate tab.

The web interface and API for Comet Server make use of a built-in web server, based on the standard library from the Go programming language. This embedded web server is secure, performant and powerful, and includes many recent features such as TLS 1.3 and HTTP/2. As this is a bundled component, any security updates for this component must be delivered as part of a Comet Server update. Recently, the HTTP/2 Rapid Reset Attack (CVE-2023-44487) made headlines around the world, affecting major corporations including Google and Cloudflare. This month, we were able to take advantage of newly available mitigations to resolve the issue directly within Comet Server.

We've also implemented additional security protections against XSS attacks, as a defense in depth measure. The Comet Server web interface now uses an extremely strict Content Security Policy (CSP) to help prevent any remote attacks on your administrator login session.


We've kept the CometCon tradition going, bringing remote and local Comet team members together for another week-long conference.

During the week, we made it a priority to focus on deep technical brainstorming and planning, with speakers from various departments. But it wasn't all work - the collaborative environment was combined with social events including decorating the office, renting out a cinema, learning to mix cocktails, taking a flight lesson, and the infamous "Mandatory Fun".

Comet 23.11.0 Saturn

We're very pleased to announce our latest Quarterly release series - Comet 23.11 Saturn.

Our product's first codename started many years ago with the planets of the inner solar system, and our Voyager track continues ever more outward into distance parts of space. Recently, all our quarterly releases have been named after moons of Jupiter. But with the recent addition of VMware support this quarter, we thought that adding a big new feature deserved a big new planet!

Saturn needs no introduction as the sixth planet from the Sun. It is the second-largest planet in our solar system after Jupiter, large enough to fit the Earth inside more than 760 times over. Its iconic rings were discovered in 1610, and we are continuing to find additional moons - over 140 have been discovered, most recently in 2020.

Comet 23.11.0 Saturn includes 8 new features and 23 enhancements that were developed over the course of the previous 23.9.x Voyager series, including our VMware Protected Item type, a lobby for silent installed devices, and improvements for Object Lock and Comet Storage.

The full list of improvements is available in the official Release Notes. If you'd prefer to listen rather than read, we're hosting a webinar next week to discuss this new quarterly release and all the new changes. Please register for a notification before we go live on December 6th (5pm EDT / 2pm PDT) to catch up on all the latest Comet news with us - and as usual, there will be time for a live question-and-answer session at the end of the presentation.

Hyper-V Backup 2.0 Announcement

We are currently working towards releasing our new Hyper-V Backup 2.0 offering next year, which means we’ll be retiring our existing Hyper-V backup at the same time. To prepare for this, we’ll preview new technology in Comet’s Voyager releases and add further capabilities to Hyper-V backup as we work towards the launch of Hyper-V Backup 2.0 in 2024!