The Automated System Recovery (ASR) is one of the aspects in Windows Vista that has been evolved with the introduction of Vista Service Pack 1. A Windows application programming interface, ASR is designed to keep track of and record the configuration of disks and volumes on a system. In the end, ASR comes into play in cases of bare metal recovery scenarios. Ahead of restoring the operating system as well as the associated content including programs and data, ASR will take the disks and volumes to their original state. The Automated System Recovery will manage disks in accordance with Critical and non-Critical labels, depending on whether they do or do not contain system state or operating system components.
“ASR in Vista and Server 2008 is tightly integrated with the Volume Shadow Copy Service (VSS) and presents a writer interface, which is a significant change from Server 2003 and XP. During a backup the ASR writer reports metadata describing all the disks and volumes on the system. During the restore the requester passes the same metadata back to the writer which recreates disks and volumes as necessary. The ASR writer will fail a restore if it cannot find or recreate all the critical disks necessary to restore all the critical volumes. Non critical disks are restored on a best effort basis and requesters may control that behavior using include and exclude options,” revealed Dinesh Haridas, Program Manager in the Storage Solutions Division.
With Windows Vista SP1, Microsoft has introduced supports for the Extensible Firmware Interface (EFI). As such the ASR in both Vista SP1 and Windows Server 2008 was tweaked in order to be capable of recovering EFI system partitions in a bare metal recovery. Haridas informed that the evolution of the ASR API was done as an integral part of the overall support for EFI based systems.
“In Vista, ASR would always recreate dynamic disks even if they had layouts identical to that during backup. With SP1 and Server 2008 that behavior has been modified so that the writer will treat dynamic disks like basic disks and not recreate them during restore if it detects that the layout is unchanged from the time of the backup,” Haridas added. “ASR in SP1 and Server 2008 supports ETW tracing which among other things is more performant and can be configured easily at run time. This makes for easier diagnostics and trouble shooting and was motivated by feedback from Vista customers.”