There are few different scenarios here; in any case I would recommend updating your BIOS (so the RAID option ROM will be updated also) and the Intel® Matrix Storage software, now called Intel® Rapid Storage Technology. Please refer to the software available from the system manufacturer’s website and take the necessary precautions for the BIOS update.
According to your description of the issue, it is possible the RAID structure metadata became corrupted. By rebuilding or recreating the RAID you will regenerate such structure and hopefully by updating BIOS and IRST as mentioned above you will prevent the issue from happening again (assuming an issue with the Intel® Matrix Storage software and the drives being physically ok).
If we consider the possibility that at least one of the drives is bad or going bad, the recommendation will be to undo the RAID or reset the disks to non-raid and run a full diagnostic test on them separately. You can usually find diagnostic software provided by the hard drive manufacturer.
Thank you for your reply. I would like to know if the drives are ok so would the best thing be to first undo the RAID or reset the disks to non-raid, as you suggest, and if so could you direct me to the instructions for that? Sorry I don't know much about these things. Do I need to take any precautions to ensure that no data is lost?
Theoretically, RAID 1 is the only type you can reset and the data will remain, because it is a mirror. If you reset a RAID 0 or RAID 5 the data will be lost. You may still consider creating another back up just in case something else happens.
Revisiting your description above I can see you are… “currently working with one drive - the other still shows a status of "failed" in the Intel Matrix Storage Console and shows "Error Occurred" on the boot screen.” This probably means the drive is already damaged.
You may enter the RAID option ROM by pressing Ctrl+I before Windows* initiates booting process. You will only be able to enter when two hard drives or more are connected to this SATA controller. Then, you will see something like this. The option Reset Disks to Non-RAID should be available there.
Afterwards, you may run a diagnostic test on each drive. Replace the failed drive if needed, boot to Windows* and use Intel® Matrix Storage (or IRST) to create the RAID again.
Creating the RAID from Ctrl+I will delete the existing information but if you use IRST in Windows* you can choose which drive to use in order to rebuild your RAID again. Do not forget to check if you can update your IRST software and BIOS.
I have followed up by seeing whether there is an update to the BIOS. The only update for my PC was released in Jul. 2010, just a few months after mine (Feb. 2010). Under Fixes and Enhancements it just says "Update INTEL Microcode per Intel request". Since I only started having problems last year, the timeline doesn't seem right and I'm reluctant to do this update if it's not necessary due to potential risks. Is it possible to find more information about this update request from Intel?
Important things first.
RAID is for redundacy and increased hardware failure tolerance, not for backup.
Every user mistake like deleting/overwriting wrong file, virus/malware and power surges like lightning bolt to power line can destroy your data because same actions are duplicated on both storage devices and overvoltage caused by lightning can fry every single part.
Backup is something which doesn't automatically receive all those actions and is "disconnected" out of reach of power surges.
1.2TB is weird size for HDD so are you sure about that?
Standard sizes are 1 and 1.5TB
One reason for array becoming degraded might be that "failed" drive hit some hard to read sectors and delay in possibly multiple slow re-reads of those sectors made RAID controller think drive failed.
Though apparently nowadays that should be more a problem of dedicated full blown hardware RAID controllers.
Thanks for your insights.
I am aware that the RAID drive is not for backup. I have just been trying to determine why it fails, or at least says it has failed but is not actually bad (as in the most recent case).
1.2TB is what my system info card from Dell says. When I go into Windows Explorer and look under properties for this drive, it says that the capacity is 586 GB. Not sure why the card says otherwise.