Calculating Repository Size for Veeam Backup

When it comes to calculating the repository size for Veeam backup, there are several factors to consider. One of the key considerations is the automatic rule that triggers the generation of a new repository file in the same storage location when reaching 59 TB. This can help counteract the limitation imposed by this rule.

The local VB365 Repository consists of multiple folders created for each year of retention. However, it's essential to note that running restore or backup processes on volumes used to store backup data while they are being encrypted or decrypted can heavily impact the performance of the Bitlocker process. Therefore, it's recommended not to run these processes in parallel.

Bitlocker encryption is fully supported and does not significantly impact backup and restore times when working with volumes storing backup data. To limit the overall backup size, you can reduce the number of item versions in document libraries and lists.

The formula for calculating repository size takes into account three main factors:

1. Total data size

2. Daily change rate

3. Days of retention

For SharePoint and OneDrive data, the formula is the same (OneDrive for Business is essentially SharePoint under the hood). The total data size refers to the planned size for storage, including growth and migrations.

To estimate the daily change rate and total source data size, you can use the following formula:

Total Data Size + (Daily Change Rate * Days of Retention) + 10% Working Area

It's essential to note that this only reflects current cloud usage and that backup on disk will be larger due to metadata and backed-up item versions.

To view current and previous data usage for SharePoint Online and OneDrive for Business, you can visit the Reports > Usage > SharePoint > Site Usage > Storage section in the Microsoft 365 Admin Center.

While processing backups, transaction protocols and database checkpoints can take up to 10% of the repository space, calculated as workspace. This factor can be also estimated with a more optimistic value of 1.5.

For normal mailbox backups, the change rate is multiplied by 2 due to archiving and file versioning, which takes up additional backup space. In the field, we typically experience daily change rates ranging from 0.2 to 1%.

To get an estimate of the size of all primary mailboxes, you can use the following PowerShell command:

Get-Mailbox | Get-MailboxStatistics | Select-Object DisplayName, ItemCount, TotalItemSize | Format-Table –autosize

You can also use this command to get the total size of current archive mailboxes using the -Archive option.

By calculating the repository size based on these factors, you can ensure that your backup storage is sufficient for your organization's needs.

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