Beyond the widespread outages, I have so many personal war stories that it's hard to pick a favorite.
My first job out of college in the mid-late 90s was at an ISP in Pittsburgh that I joined pretty early in its existence, and everyone did a bit of everything. I was hired to do sysadmin stuff, networking, pretty much whatever was needed. About a year after I started, we brought up a new mail system with an external RAID enclosure for the mail store itself. One day, we saw indications that one of the disks in the RAID enclosure was starting to fail, so I scheduled a maintenance window to replace the disk and let the controller rebuild the data and integrate it back into the RAID set. No big worries, right?
It's Tuesday at about 2 AM.
Well, the kernel on the RAID controller itself decided that when I pulled the failing drive would be a fine time to panic, and more or less turn itself into a bit-blender, and take all the mailstore down with it. After a few hours of watching fsck make no progress on anything, in terms of trying to un-fsck the mailstore, we made the decision in consultation with the CEO to pull the plug on trying to bring the old RAID enclosure back to life, and focus on finding suitable replacement hardware and rebuild from scratch. We also discovered that the most recent backups of the mailstore were over a month old :(
I think our CEO ended up driving several hours to procure a suitable enclosure. By the time we got the enclosure installed, filesystems built, and got whatever tape backups we had restored, and tested the integrity of the system, it was now Thursday around 8 AM. Coincidentally, that was the same day the company hosted a big VIP gathering (the mayor was there, along with lots of investors and other bigwigs), so I had to come back and put on a suit to hobnob with the VIPs after getting a total of 6 hours of sleep in about the previous 3 days. I still don't know how I got home that night without wrapping my vehicle around a utility pole (due to being over-tired, not due to alcohol).
Many painful lessons learned over that stretch of days, as often the case as a company grows from startup mode and builds more robust technology and business processes as a consequence of growth.
jms