Escape windows repair install and start in normal boot

when you upgrade the raid controller firmware, you must make certain you have updated the storage driver first. Otherwise there's a chance that the older driver will not recognise the controller after the update, which always leads to a BSOD.

You can try to boot from a liveCD (RHEL or CentOS preferrably, since Dell have linux update packages for RHEL, which you can download to the liveCD and run), downgrade the firmware to the old version, and try to boot your OS again.

If that doesn't help, a LiveCD can be used to salvage the data from the system, before a proper reinstall.

Pulling the power causes everything to stop in flight, with no warning. kill -9 has the same effect on a single process, forcefully terminating it with a SIGKILL.

If a process is killed by kernel or power outage, it doesn't do any clean-up. That means you could have half-written files, inconsistent states, or lost caches. You usually don't have to worry about any of this because of journaling, exit status and battery backup.

Temporary files in /tmp will be automatically gone if they are in tmpfs, but you may still have application-specific lock files laying around to remove, like the lock and .parentlock for firefox.

Most software is smart enough to retry a transaction if it doesn't record a successful exit status. A good example of this is a typical mail system. If a message is being delivered, but gets cut off in the middle, the sender will retry later until it gets a success.

Your filesystem is probably journaled. If you are moving or writing a file and it dies mid-stream, the journaled file system will still reference the original. The journaled filesystem will make changes non-destructively, leaving the old copy, then only reference the new copy as a last step before reclaiming space the old copies occupied on disk.

Now if you have a RAID array, it has all kinds of memory buffers to increase performance and provide reliability in a power failure. Most likely your filesystem will not know about the caches in the device and their state, so it thinks a change has been committed to disk, but it is still in the RAID cache somewhere. So what happens when the power dies? Hopefully you have a functional battery in your RAID enclosure and you monitor it. Otherwise you have a corrupt file system to fsck.

Yes, a few bits can become corrupted in a binary, but I would not worry about that much on modern hardware. If you are really paranoid, you can monitor the health of your disks and RAID with the appropriate tools, but you should be doing that anyway. Do regular backups and get an Uninterruptible Power Supply.