Slow restore speed directly from AWS S3 bucket

[dariusz.tyka]

Case ID: 07990860
We are using Veeam AfW to backup our physical servers running Windows Server 2022 OS.
We have different backup jobs pointing either to local storage for short term retention and AWS S3 bucket for long term retention. We have 2x 10Gbit links to AWS. During backup we are utilizing up to 2-3Gbps. Unfortunately during restore sessions (FLR) I see only 10-15MB/s usage of our 10Gb links. It doesn't matter if I restore small files or single few GB in size file. Restore speed is similar. So restoring several TB of data with slow speed will be time consuming task.
When I try to download files directly from S3 bucket to mentioned servers using other tools like AWS CLI or S3Bowser I can see much higher link utilization (up to 3-3.5Gbps) than during restore session.
Those are standalone Agents not managed by Veeam B&R server. Servers are very well equipped (64 or 128cores), 512GB of RAM, SSD drives.
Can you advice how to improve restore performance?

[Mildur]

Hi Dariusz,

Please continue working on this together with our support team — performance issues are not something we can troubleshoot through a forum post (as outlined in our forum policies).
Let’s wait for the conclusion from our support team, and depending on the outcome, we can decide if RnD teams has to be involved or not.

Thanks,
Fabian

[dariusz.tyka]

This is the response I got from Veeam support:
Thank you for your patience! The only action that may improve File Level Restore performance is changing the block size from 1 MB to 4 MB. However, this will impact compression and deduplication.
WindowsFLR is a single-threaded process, while uploading data during the Backup Job is a multi-threaded process - that's why the upload speed is a lot higher than the FLR download. The smaller the blocks, the more metadata is sent in between. Unfortunately, given the architecture, if a lot of information needs to be restored, it may be faster to perform a Volume-Level restore rather than a File-Level Restore.

Is this really true? Nothing can be done to improve FLR beyond 15MB/s?