Q: I'm trying to use Azure Site Recovery to protect a local virtual machine to Azure. However, I'm receiving an error message that says my OS disk is larger than 127GB. What's wrong?
A: The maximum OS disk size for an Azure virtual machine is 127GB. Any OS instance that will be migrated to Azure or needs to fail over to Azure in case of a disaster needs to fit within the supported limits for an Azure virtual machine. Therefore, if the OS disk is larger than 127GB, then replication/migration to Azure won't be possible. The solution is to resize the OS disk to 127GB or smaller. If it's is a virtual machine, you can use the Microsoft Management Console (MMC) Disk Management snap-in to shrink the VHD (or VMDK) disk after shrinking the actual volume sizes within the OS instance. If you can't shrink to 127GB or smaller because there's too much data, move the data to a separate disk to allow the OS disk to be 127GB or smaller; data disks can be up to 1TB (1023GB; that's not a typo) in Azure, and the number of data disks supported varies depending on the size of the Azure virtual machine.