While trying to run ExportSite on ArgisServer fails with "Export operation failed. null" message. ArcgisServer is linked with a pair of HA DataStores. Any help would be appreciated
What version are you using? There's a bug fixed at 10.6 where corrupt/missing thumbnails would cause exportSite to return a similar, but not identical error. Can you run the export with DEBUG logs and see if any more information is logged?
I just ran into the same error this morning while making a backup with webgisdr tool.
The ArcGIS Server failing was the hosting one.
Took me a while to find out the root cause because the error logged was not very talkative but I finally found it: after a reboot of the VM, the drive hosting the "arcgiscache" folder was not mounted thus inaccessible. After mounting it back, the issue was solved.