I was recently setting up another mailbox database target within an existing DAG and found that my database copy kept failing with the following error:[error]The log copier was unable to continue processing for database ‘MAILBOX_DB\SERVER’ because an error occurred on the target server: Continuous replication – block mode has been terminated. Error: the log file sector size does not match the current volume’s sector size (-546) [HResult: 0x80131500]. The copier will automatically retry after a short delay.[/error]This was odd especially as the server in question was a VM however after some further troubleshooting it transpires to be an issue if you have one member on a VHD file and another (my new server) running on a VHDX file. These two different Virtual Hard Disks file formats lead to minor differences in the file systems contained within them which is enough to cause replication issues on Exchange DAG’s.The following command can be run on each server and the output compared.fsutil fsinfo ntfsinfoJust for completeness, this issue can also be expressed on wildly different disk arrays and storage hardware drivers.