What made my FreeBSD server freeze?

[Ivan Voras]

On 08/30/10 13:24, peter at vfemail.net wrote:
>
> When I awoke this morning my FreeBSD box was frozen -- completely unresponsive at the console -- and displayed these messages on the console:
>
>       ad0: READ command timeout tag=0 serv=0 -resetting
>       ata0: resetting devices
>       ad0: removed from configuration
>       done
>       Aug 30 03:09:25 abc sm-mta 88427 xyz SYSERR(root): collect: Cannot write: ./xyz (fsync uid=o, gid=25): Device not configured
>
> The box has been in continuous operation for years, and I've never seen this behavior before.
>
> I rebooted the machine this morning and, thank God, it came back to life.
>
> Is this an early warning that the hard drive is failing and should be replaced this week?

Very probably!

> Is there anything else I should explore or do at this time?

If not the drive, check drive cables, the power supply and 
motherboard/CPU overheating.