When continuing the VHD backups of Windows machines after their restarts UrBackup is perfroming read/write operation on the destination drive making the backup slower

First of all, I’m a happy UrBackup user - thanks for the amazing work!

I’ve been using it on Windows 2019 Server (2.5.26) and doing full images only backups (VHD) of Windows machines (2.5.19). Backups are kept on an iSCSI volume (RAID10 on Ubuntu Server) and the volume is formatted to ReFS and the deduplication savings are amazing - more than 85% percent!

The thing is, when the machine that is doing the backup is turned off the UrBackup simply sits an wait for it to come back online. Once it does the backup continues but this time the progress is noticeably slower. By looking at the Resource Manager on Window 2019 it’s visible that the difference is that now there is a lot of read/write operations on the target VHD file instead only write operations as before and at least two processes involved: “System” (which only writes) and urbackup_srv.exe (read/write). At the same time Resource Manager for the backup of the machine that hasn’t been restarted shows only write operation done by “System”.

If anyone has any idea whet might be the cause it would be greatly appreciated.