A rack-mounted Windows Server 2019 host boots from a mirrored pair of 600 GB SAS drives on a hardware RAID controller. After the host is shut down so a second SAS tape drive can be attached to an unused internal HBA port, the system powers back on and POST completes with no errors. Instead of loading Windows, the console displays the message "Operating System not found". From the RAID BIOS utility the virtual disk that contains the OS is reported as Optimal, and both physical drives show healthy SMART data. No other configuration changes were made.
Which of the following is the MOST likely reason the server will not start the operating system?
The tape drive negotiates a different SAS link speed, preventing the RAID controller from initializing its disks.
The master boot record on the mirrored system partition became corrupted and must be rebuilt.
The RAID controller disabled write-back caching because its battery module is depleted.
The firmware boot order was automatically changed so the system now tries to boot from the newly attached tape drive controller.
Because a new bootable device (the tape drive's HBA) was added, the system firmware automatically moved that controller to the top of the boot list. The server is therefore attempting to boot from the tape drive, which has no boot sector, and immediately returns the "Operating System not found" error. Selecting the RAID virtual disk as the first device (or removing the tape drive during boot) restores normal start-up.
Incorrect answers:
Depleted RAID cache batteries disable write-back caching but do not prevent the controller from presenting a valid boot sector.
Mismatched SAS link speeds can reduce performance or prevent a device from coming online, but the RAID array is already reported as Optimal and healthy.
A corrupt MBR could cause the same message, but nothing was written to the disks; only the addition of new hardware occurred, making a firmware boot-order change far more likely.
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Why did the firmware change the boot order after adding the SAS tape drive?
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What steps should be taken to fix the boot issue caused by the tape drive?
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Could adding other hardware cause similar boot issues? How can this be prevented?