Office 365 - Performance Considerations
The backup job uses the Microsoft Office 365 API to read data from the cloud and store it in the Storage Vault. A large amount of data is downloaded to the local device during a backup, so job duration depends on both the volume of data and the limits Microsoft applies to the API.
Incremental backups and server-side delta change
The backup job takes advantage of Office 365 server-side delta change APIs to efficiently perform incremental backup jobs.
- This applies to Mailbox (email), Calendars, Contacts, OneDrive files, and Teams files, allowing for high-performance incremental backup. Deleting any file from within a backup job snapshot will disassociate that snapshot from the server-side delta change. If you delete a file from the most recent backup job snapshot, the next incremental backup job will require a longer duration.
- This does not apply to SharePoint lists, which may re-download data during each backup job, reducing performance.
API rate limiting
The Office 365 API imposes some rate-limiting on the backup operation, which may limit the total performance of the backup job.
- One of the imposed rate-limit rules is based on the target mailbox account, and each mailbox has its own rate limits. Magnus Box backs up multiple mailboxes in parallel. If the Office 365 tenant has a large number of mailboxes, the overall backup job performance is balanced evenly across all the mailboxes. If the tenant contains mailboxes with very different sizes, the single largest mailbox may reduce performance owing to the tail effect: the job cannot finish until the slowest, largest mailbox completes.
Reducing latency to Office 365
Hosting the Magnus Box device inside Microsoft Azure provides the lowest possible latency to the Office 365 servers, improving performance.