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Windows 2008 R2 is unable boot up after a full OS restore

Windows failed to start. A recent hardware or software change might be the cause. To fix the problem:

1. Insert your Windows installation disc and restart your computer.
2. Choose your language settings, and then click "Next."
3. Click "Repair your computer."

If you do not have this disc, contact your system administrator or computer manufacturer for assistance.

Status: 0xc000000e

Info: The boot selection failed because a required device is inaccessible.

Windows 2008 R2 is different in nature from Windows 2008 in many significant ways.  One particularly significant difference is how a standard installation partitions available disk space.  By default, when installing Windows 2008 from DVD, the unallocated space which is subsequently allocated for the C:\ drive is entirely allocated to C:\.  However, by default, when installing Windows 2008 R2 from DVD, the unallocated space which is subsequently allocated for the C:\ drive is actually broken up into 2 partitions.  One partition is a 100 megs in size and the remaining space becomes C:\.  The 100 meg partition is a System Partition and remains unnamed (no drive letter is assigned) and it contains OS boot files.

The two partitions can be seen by running "mountvol" from the cmd line or by using the Disk Management interface.

Example mountvol output:
Possible values for VolumeName along with current mount points are:

   \\?\Volume{3c1646a6-0548-11df-b47a-806e6f6e6963}\    <---- this is the 100 meg unnamed partition
       *** NO MOUNT POINTS ***




Example as observed in Disk Management:

Although creating the 100 meg System Reserved partition is the default install behavior of Windows 2008 R2, it is possible to architect an install which omits the 100 meg System Reserved partition by manually partitioning and naming the C:\ volume prior to installing Windows 2008 R2 from DVD.  Some automated build environments can cause a Windows 2008 R2 OS to have only a single partition as well.

When the unnamed 100 meg System Reserved partition does not exist, the Windows 2008 R2 installation places the boot files onto the C:\ drive into a hidden folder called 'boot'.

When NetBackup backs up a standard installation of Windows 2008 R2, it taps into the unnamed System Partition to backup the boot files by using the VSS Writer called Automated System Recovery or "ASR Writer" which can be seen when running 'vssadmin list writers' from the cmd prompt.

Writer name: 'ASR Writer'
  Writer Id: {be000cbe-11fe-4426-9c58-531aa6355fc4}
  Writer Instance Id: {59a930b6-c859-40a2-b2a3-c6d467f70cb6}
  State: [1] Stable
  Last error: No error

When a full OS Backup / Restore occurs on a standard installation of Windows 2008 R2 which has the unnamed System Partition, there should be no problems booting up afterward as the ASR Writer correctly reads and writes the needed data to the boot location and no GUID (Globally Unique Identifier) corruption occurs.

However, when the \boot\ folder exists on a named volume like C:\ the the \boot content is backed up by the file system in addition to being backed up by the ASR Writer.

During a restore operation, the \boot\ content is first restored from the ASR Writer backup and then restored again from the C:\ backup which causes an inconsistency in the drive GUID definitions within the \boot data which leads to the boot error.

In a DR Test or in an actual DR Scenario, when using NetBackup to perform a full OS recovery, it is required that the same partition structure exist on the newly built destination OS.  In an actual DR Scenario, it may be impossible to know if the original Windows 2008 OS had the 100 meg unnamed System Reserved partition.  

There are two methods to avoid the problem on boot:
1. When performing a full OS recovery, check for the presence of C:\boot when in Backup Archive and Restore, and if C:\boot exists, simply exclude it before initiating  the full OS restore of Windows 2008 R2.

2. Plan ahead.  For Windows 2008 R2 clients on which C:\boot resides due to the absence of the 100 meg unnamed System Partition, add a client-side exclude to prevent C:\boot from getting backed up.

If you have encountered a boot problem where you suspect this is the root-cause, it may be possible to recover from the error and boot normally if by following these steps:

1. Insert the Windows 2008 R2 DVD and reboot.  
2. Press a key when you see "Press any key to boot from CD or DVD..."
3. Select Next > Repair your computer
4. Select Next > Command Prompt

bcdedit to see if the values for Windows Boot Manager > Device and Windows Boot Loader > Device and osdevice are set tounknown

If they are set to unknown, run these three commands to correct the settings, and reboot:
bcdedit /set {DEFAULT} device partition=c:
bcdedit /set {DEFAULT} osdevice partition=c:
bcdedit /set {BOOTMGR} device partition=c:


cd into X:\sources\recovery and run StartRep.exe  to launch a quick automated startup repair utility which corrects boot environment values.

NOTE: The first boot after doing a full OS restore of Windows 2008 or Windows 2008 R2 may take 5-10 minutes or longer.  It may show a blank screen during this time.  The machine is not hung.  Do not reboot forcefully during this time, as it may corrupt the OS causing it not to boot up.  The slow boot is due to a bulk file-rename for files which were restored with temporary file names because their production counterparts were active and locked at the time of the restore.  This also happens with Windows 2003, but the file-set is much smaller and the boot-lag is therefore much shorter in duration.
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