Boot Error on FreeBSD/i386

Hi all,

I am a complete novice at FreeBSD, and I have a boot error on a node server in a cluster that runs FreeBSD. The error message is as follows:


What I am wondering is what does error 7 lba 0 refer to? Thanks in advance for your help.
Most likely cause is a bad block on one of the disks in the machine, probably ad7. Time to replace the disk and restore the machine from backups.