This community-contributed blog post shows how MSPs in the community are using Corso to build out a multi-tenant backup solution for their Microsoft 365 customers. If you have questions, come find the author (or us) on the Corso Discord.

In Part 1 we discussed how there’s more than one way to run backups, and how full and incremental backups differ.

With all the background information out of the way, it’s time to see how incremental backups are implemented in Corso. To do this, we’ll discuss things in the context of a running example.

Full Microsoft 365 backups can take a long time, especially since Microsoft throttles the number of requests an application can make in a given window of time. Recent additions to Corso have reduced the duration of backups after the first backup by taking advantage of Microsoft’s delta query API. Doing so allows Corso to retrieve only the changes to the user’s data since the last backup instead of having to retrieve all items with the Graph API. However, implementing backups in this manner required us to play a few tricks with the Corso implementation, so we thought we’d share them here.

I was inspired by some recent conversations with Corso users on Discord, and this Reddit thread, to talk about the ideal cadence for backups.

Why do we need backups again?​

I know you’re here at the blog for Corso, a Microsoft 365 backup tool, so you probably don’t need to be sold on the necessity of backups. But just as a reminder, the Microsoft Shared Responsibility Model, similar to that of all public cloud providers, means there’s a place where their responsibility to help you with recovery stops.

When we evaluate malware threats, we often think mainly of protecting our users. The biggest concern is always going to be lost availability and leaked data if malware affects our system. But like any threat with an infection model, part of the story is about your responsibilities as an operations engineer to keep others safe.

Recently when writing about the storage options for Corso, I found myself going pretty far in the weeds on storage classes in S3. I thought I’d make a list of all the storage options and why they might, or might not, work for backups.

Each day, you and your colleagues put hours of work into creating, sending, and receiving all kinds of critical data: hundreds of emails, Word documents, spreadsheets, and more. You and your company want to protect your data from everything that could go wrong, such as server outages, cyberattacks, accidental deletions and anything that could cause you to lose valuable work, time, and money. Even small instances of data loss cost businesses an average of between $18,000 and $35,000 – and that’s with losses of fewer than 100 files! That number can grow into the millions for large-scale losses and breaches.

My question to you is, how can you protect your data without spending countless hours and thousands of dollars?

I recently sat down to talk with Demetrius Malbrough on a recent episode of his Data Protection Gumbo podcast. We covered several topics related to data protection for SaaS services in general and M365 specifically as well as the role of open source tools like Corso can play to help secure this data. I have summarized some of the key discussion points below, but I highly recommend listening to the full episode. Also, if you aren't following the podcast and Demetrius already, you should!

Corso, an open-source tool for backing up Microsoft 365 Data, was lucky to have Kias Hanifa, CTO at Fonicom, extensively test it. He was kind enough to write this guest post

I’d like to tell the story of how Corso is helping us build a more reliable experience for our clients. To start with, a word about my company:

Corso is a free and open-source tool to back up your Microsoft 365 or Office 365 data. For Microsoft Office 365 administrators, it backs up user data to any S3-compliant storage. Leaving you in control of when your data is backed up, and how it’s restored.