On Tue, Feb 23, 2021 at 5:14 PM Justin Streiner <streinerj@gmail.com> wrote:
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.

Oh, dear. RAID.... that triggered 2 stories.
1: I worked at a small ISP in Westchester, NY. One day I'm doing stuff, and want to kill process 1742, so I type 'kill -9 1' ... and then, before pressing enter, I get distracted by our "Cisco AGS+ monitor" (a separate story). After I get back to my desk I unlock my terminal, and call over a friend to show just how close I'd gotten to making something go Boom. He says "Nah, BSD is cleverer than that. I'm sure the kill command has some check in to stop you killing init.". I disagree. He disagrees. I disagree again. He calls me stupid. I bet him a soda.
He proves his point by typing 'su; kill -9 1' in the window he's logged into -- and our primary NFS server (with all of the user sites) obediently kills off init, and all of the child processes.... we run over to the front of the box and hit the power switch, while desperately looking for a monitor and keyboard to watch it boot. 
It does the BIOS checks, and then stops on the RAID controller, complaining about the fact that there are *2* dead drives, and that the array is now sad.....
This makes no sense. I can understand one drive not recovering from a power outage, but 2 seems a bit unlikely, especially because the machine hadn't been beeping or anything like that.... we try turning it off and on again a few times, no change... We pull the machine out of the rack and rip the cover off. 
Sure enough, there is a RAID card - but the piezo-buzzer on it is, for some reason, wrapped in a bunch of napkins, held in place with electrical tape. I pull that off, and there is also some  paper towel jammed into the hole in the buzzer, and bits of a broken pencil....

After replacing the drives, starting an rsync restore from a backup server we investigate more....
...
it turns out that a few months ago(!) the machine had started beeping. The night crew naturally found this annoying, and so they'd gone investigating and discovered that it was this machine, and lifted the lid while still in the rack. They traced the annoying noise to this small black thingie, and made poked it until it stopped, thus solving the problem once and for all.... yay!





2: I used to work at a company which was in one of the buildings next to the twin-towers. For various clever reasons, they had their "datacenter" in a corner of the office space... anyway, the planes hit, power goes out and the building is evacuated - luckily no one is injured, but the entire company/site is down. After a few weeks, my friend Joe is able to arrange with a fire marshal to get access to the building so he can go and grab the disks with all the data. The fire marshal and Joe trudge up the 15 flights of stairs.... When they reach the suite, Joe discovers that the windows where his desk was are blown in, there is debris everywhere, etc. He's somewhat shaken by all this, but goes over to the datacenter area, pulls the drives out of the Sun storage arrays, and puts them in his backpack. They then trudge down the 15 flights of stairs, and Joe takes them home. We've managed to scrounge up 3 identical (empty) arrays, and some servers, and the plan is to temporarily run the service from his basement...

Anyway, I get a panic'ed call from Joe. He's got the empty RAID arrays. He's got the servers. He's got a pile of 42 drives (3 enclosures, 14 drives per enclosure). Unfortunately he completely didn't think to mark the order of the drives, and now we have *no* idea which drives goes in which array, nor in which slot in the array.... 

We spent some time trying to figure out how many ways you can arrange 42 things into 3 piles, and how long it would take to try all combinations.... I cannot remember the actual number, but it approached the lifetime of the universe....
After much time and poking, we eventually worked out that the RAID controller wrote a slot number at sector 0 on each physical drive, and it became a solvable problem, but... 


W


jms

On Tue, Feb 16, 2021 at 2:37 PM John Kristoff <jtk@dataplane.org> wrote:
Friends,

I'd like to start a thread about the most famous and widespread Internet
operational issues, outages or implementation incompatibilities you
have seen.

Which examples would make up your top three?

To get things started, I'd suggest the AS 7007 event is perhaps  the
most notorious and likely to top many lists including mine.  So if
that is one for you I'm asking for just two more.

I'm particularly interested in this as the first step in developing a
future NANOG session.  I'd be particularly interested in any issues
that also identify key individuals that might still be around and
interested in participating in a retrospective.  I already have someone
that is willing to talk about AS 7007, which shouldn't be hard to guess
who.

Thanks in advance for your suggestions,

John


--
The computing scientist’s main challenge is not to get confused by the
complexities of his own making.
  -- E. W. Dijkstra