Exchange item live restore 300 times slower than PST export

[knut-weber]

A customer deleted 60 thousand items in one folder. Single item restore was stopped after one day and about 60% finished because it blocked new backups.
A second trial with export to PST of this folder endend after 8 minutes with a 6 GB PST successfull!

This cannot be a backup issue as we used PureStorage Storage snapshots which were generated both inside and outside veeam backup jobs and were loaded into veeam Explorer for Exchange.
It has to be an issue regarding the EWS API into a running Exchange mailbox versus exporting with Outlook 64 Bit streaming into PST on a block device.

It is interesting because the EWS API is the only available in O365 for backup and restore. Regardless of the throttling policy it seems to scale not very good with the number of items.
Has anyone the same experiences with EWS vs. PST? We even have customers with hundredthousands ob objects in one Mailfolder. Don´t ask - they are programming workflows this way

[Gostev]

Hello, please include support case ID for this issue, as requested when you click New Topic. Otherwise, this thread will be removed by moderators. Thanks!

[knut-weber]

Case # 03906501 - but this was a general question, no specific case.

[knut-weber]

The user used for backup had assigned an old and forgotten SymantecEWSRestoreThrottlingPolicy.
If anyone finds this useful.
found with Get-ThrottlingPolicyAssociation