I submitted this as a GitHub issue last week.

TL;DR: Backblaze aparently doesn't support those flags that are enabled by default
"Backblaze does not yet accept these headers, so we recommend downgrading to AWS Javascript 3.x SDK version 3.728.0."

https://github.com/vatesfr/xen-orchestra/issues/8358

cloudrootab created this issue in vatesfr/xen-orchestra

open S3 Backup: "Unsupported header 'x-amz-checksum-mode' received for this API call." #8358

@olivierlambert
I've finally had time to sit down and do some more troubleshooting.
It seems that the issue is somehow tied to the backup-jobs themselves.
Deploying XOA and subsequently importing XO-config from my XOCE instance. I continued to see several issues between both instances.
These issues pretty much went away, when I re-did the backup-jobs from scratch. And are now much more in-line with what I'm excepting to see. This was done on both XOA Stable, Latest and XOCE

I am no longer able to repoduce this at all.
So my guess is that a bug of some sort got introduced with this being a constantly updated from source instance.

Marking as solved. As I don't believe there is much more to do at this time.

@McHenry
Differences could be things such as:

• Amount of cores between hosts for migrations
• Guarantee performance between guests. So that they don't affect each other as much.

Same with overprovisioning dynamic RAM