entropy
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January 2008


4 Jan 2008 [link to here]
Vegas road trip

A friend and I drove to Las Vegas for a few days. Both of us had seen it briefly in passing but hadn't really been there before. It's a freakish place. My overall impression was that someone had seen Disney World and said, "This is a fine idea, but the centralized command structure is un-American. Let's redo this with an open set of autonomous agents organized by a market economy. And not so much for the kids." I imagine that's what everyone thinks when they see Vegas for the first time.

We saw two Cirque shows: Zumanity and O. Zumanity sucked. It was supposed to be Cirque plus sensuality, but instead it was Cirque plus crass clowns and wasn't sensual or interesting. It had a few good acrobatic routines, but they couldn't salvage the show.

O, on the other hand, was phenomenal. Someone told me it doesn't live up to the hype, but if that's the case, the hype must be tremendous because I thought the show was excellent, and I'm pretty jaded. It was definitely a Cirque show, with all the over-the-top pomp that implies, but it had a unique stage and routines that took excellent advantage of it.

Blue Man Group was excellent. I saw it 15-20 years ago in NY and it was pretty much the same show, but it was great fun regardless. Creative routines, good physical comedy, and great music and visuals.

We caught a faux-Beatles show ("Fab Four"), which was ok. There's nothing wrong with live performance of music I enjoy, but under normal circumstances, I'd be disappointed to pay $50 for a merely adequate concert.

That was it for the organized entertainment. We rode the monorail a few times (for transit, not purely for entertainment), but mostly did a lot of walking up and down the strip and into many casinos. The Venetian wins our awards for best architecture and best pizza. (We had a tough time finding meals in between fast food and $50/plate fancy dinner, and the service was universally awful.) I'd sad to report that the MGM lions were not interested in my laser pointer.

I also rode the NASCAR Speed Ride at the Sahara, a super fast super short roller coaster. And by "rode", I mean "rode six times" (four during the day, then two later that night). The initial acceleration is the best part. On their web site, they list some specs: 0-45mph in 2 seconds, 70mph max speed, 3.5G acceleration, total ride time 45 seconds. There was no line except for the very front car (which was definitely the best), so it was easy just to go a bunch of times.

Even better than the roller coaster was the indoor sky diving. It wasn't really very much like skydiving, but it wasn't much like anything else either. You wear goggles, earplugs, a helmet, and the floppiest clown suit ever made, then you walk into a room whose floor is an open wire mesh trampoline above a jet engine. Flyers take turns soloing with one teacher/wrangler. My teacher, Mike Snyder, was awesome, so ask for him if you go. He gave me lots of technical instruction at exactly the level I wanted and more clearly than I expected, even when he was reduced to hand signals. One of these places opened up recently in Union City and I plan to check it out.

We also went to a gun range and fired a few clips with an AK-47 and an MP5, just for the novelty. As you might expect of a machine gun, it was all over pretty quickly, especially since the operation there (5km from the strip) was nicely optimized to maximize throughput of silly tourists like us.

One of the benefits of driving there, in addition to avoiding the Kafkaesque absurdity of modern air travel, is that we could see other things along the way. These included Hoover Dam, highway signs for Zzyzx, and the delightful tar pits of Los Angeles, all highly recommended.


18 Jan 2008 [link to here]
the power of backups

About six months ago, I bought a new laptop. For $20 extra, it has 1GB of flash hiding inside somewhere, which I was hoping I might be able to access like an ordinary external storage device. I had a plan for it. I haven't gotten around to doing anything about that plan, so I thought maybe I'd at least write it down for posterity.

First, some background. Keeping a hard drive spinning takes a significant amount of power. (Especially significant when running off batteries.) Replacing the hard drive with solid state storage might be a great solution someday, but for now it's still too expensive. One common tradeoff is to spin the drive down when you're not using it and tweak your system to need it as little as possible. One such tweak is to increase the dirty buffer flush timeout so that when you try to write something to the drive, the system holds off a while so that if you decide to write more, it can do both at once and only spin the drive up for a single short burst. The drawback is that if your system crashes before it gets around to writing those changes to disk, they're gone forever. My approach to saving and backing up approaches clinical OCD levels, so I'm not a big fan of my machine not writing things to disk when I tell it to.

So here's my crazy, as yet unrealized plan for the flash storage: whenever my laptop switches to battery power, it mounts a fan-out filesystem on top such that every write goes to both the hard drive and to an otherwise empty filesystem on the flash, then increases its hard drive's dirty buffer flush timer to, say, 30 minutes, and sets the drive to spin down quickly. When it gets back to grid power, resets the timers to normal levels, flushes the buffers, unmounts the fan-out shim, and wipes the flash. This would let me keep the drive spun down unless I need to read something that wasn't already cached, but writes would go somewhere persistent and I wouldn't lose any data in a crash. Recovering the data might be as simple as copying the flash to the hard drive. There might be complications that make automated recovery difficult, but you'd at least have a copy.

One reason I haven't done this yet is that UnionFS doesn't support fan-out where writes go to each underlying copy, only where they go to a single one. There are other union-mount filesystems, and maybe one does what I want, but I haven't looked very hard.

Another option would be to keep a copy of the ext3 journal on the flash, but I know even less about how to set that up or how I'd use it for recovery.