Blogs

I've been playing piano a little more recently; nothing ambitious, just fooling around. It improves my mood a lot; I should play more.

I rode to and from work today. My knees don't seem to be bothering me particularly any more. I try to stretch after my ride, and walk around a little more often at work. Maybe that helps.

I did absolutely nothing even slightly halloween-y today. Terrible!

My friend and co-worker Fred was back to work today after three weeks of paternity leave. He looked alert enough, and says he's actually getting 6 hours of sleep a night. I seem to be of an age when everyone I know has a baby.

I rode my bike home from work. One of the pair of cheap halogen headlights I use was dimming, though I'd recharged all the batteries just a couple days ago. I suspect a problem with the charger. It's the time of year when I'm always returning home in the dark.

I have some fairly tedious debugging to do which mostly involves waiting for compiles, so figured I"d stay up a little late and do some reading.

Stephen Tweedie's "Journaling the ext2fs Filesystem" talks about the design of ext3. It's kind of suprising, but it turns out that one of the most important features of a filesystem is the way it recovers from crashes. Keeping your files safe, after all, is probably the most important thing your computer does--a computer that regularly loses your files, or, possibly worse, silently corrupts them in ways that you don't notice till long after the fact, can be worse than useless. And crashes are hard to avoid--even if the software is perfect, there are always power outages.

So the filesystem has to be updated in a way that allows the computer to figure out what happened even if it last died halfway through an update. Also, the computer has to be able to figure out what happened *fast*. The traditional filesystem repair process can require reading through an entire filesystem, and disk sizes are growing much more quickly than disk bandwidth, to the point where reading through a large filesystem can take hours.

The approach taken by ext3 is a fairly common solution called journaling; the filesystem appends a record of each update to a special file called a journal. After it has recorded the update to the journal, it appends some kind of special "commit" marker to the journal, and only then does it go mess with the actual file system.

Once the actual filesystem has been modified, the OS is free to remove the relevant entries from the journal.

Then on reboot the filesystem just reads through the journal, performs any updates that are marked as committed (in case they weren't previously finished), and removes any entries that aren't marked as committed. (Those updates will then be lost, but that's better than possibly making a mistake and leaving the filesystem in an inconsistent state.) Recovery is fast as long as you keep the size of the journal down.

Journaling also made it easy for the linux developers to maintain backwards compatibility with ext2--it's still possible to mount an ext3 filesystem as an ext2 filesystem by just ignoring the journal.

They note one interesting connection with NFS: NFS performance is often bound by the amount of time it takes the server to synchronously commit updates to disk. With some tuning the journalling may help by turning most such commits into sequential writes to disk?

They've been promising to move the Polhemus House across town for weeks now, and it seemed it might finally happen today. I think it sounds like great fun to watch them move a two-story house up Division, across the Broadway Bridges, to its final resting place on the north side, so I walked downtown this morning to go see what progress there had been.

But, not for the first time, I was disappointed. It's still sitting on wheels next to its original lot. According to the kid I talked to, there with an adult taking pictures, Detroit Edison was just to busy handling calls (maybe a result of yesterday's crazy winds?).

So I had a hot chocolate at Eastern Accents and then did a little grocery shopping on my way home.

Sara and I finished watching "The Terminal" over dinner last night. I checked it out in part because there was an article in the International Jugglers' Association magazine a while back about Kumar Pallana, which made him out to be an interesting character. His part in "The Terminal" is indeed a highlight of the movie.

I also went to juggling yesterday, then had dinner with Dave, Paul, and Micah at Saigon Garden afterwards.

Today I walked in by way of the farmer's market (total haul: one spaghetti squash, one cauliflower, and some pears, grapes, and brussel sprouts).

Work went OK.

I biked home by way of the library (adding to the load a CD by "Les Nubiens" and a DVD of "The Terminal").

I went to work. I came home. I ate dinner.

On the way home, I stopped by the coop and the Indian place at the south end of Broadway and picked up some food; we had a premade microwaveable indian thing for dinner with some rice that Sara started in the rice cooker this morning.

We've been watching some of Leonard Bernstein's "Young People's Concerts" over dinner--Sara found them on DVD at the library. His history on the "What is American Music?" episode that we saw tonight seems a little suspect--why does the "we" he keeps referring to as making up America always mean just white people, and how does jazz spring out of nowhere?--but other than that they're well done, and have lots of fun musical tidbits.

I'm mostly over my cold, but still sniffling.

My personal Most Depresssing Books List:

1. "Survival in Auschwitz", Primo Levi
2. "The Genocides", Thomas Disch
3. "Never Let Me Go", Kazuo Ishiguro

The Ishiguro is this morning's addition; I stayed in bed another hour or two to finish it.

I finished Richard Dawkins' "The Ancestor's Tale" recently. Well worth the read. A few things that are confusing to someone with my background:

1. Family trees are not trees, because everyone has two parents. (Duh!)
2. "X and Y are members of the same species" is not a transitive relationship. There are examples of species X₀, X₁, ..., X_n such that X_i and X_i+1 interbreed for all 0 ≤ i < n, but X₀ and X_n do not.

Actually, "species" turns out to be a much more fuzzily-defined term than you'd think. There are species that probably could interbreed, but are considered separate just because they never do. Biologists also insist on putting individuals together in groups even when they never interbreed (because they reproduce asexually). Etc., etc.

I spent entirely too much of the morning trying to tweak my apache2/mod_php configuration to get drupal running again. (I have no idea how it stopped in the first place.) I couldn't find anything wrong except that whenever I asked for fieldses.org/blog in firefox, it tried to give me the source of the php script.

Eventually I figured out what was happening: I'd fixed the problem long ago, and firefox was just caching the wrong result. I don't know how to force firefox to load the new thing in that case.

We finished "Shaolin Soccer" over dinner last night. Highly recommended. If you watch it on DVD, I'd go for the "Original Chinese Version"--the U.S. version seemed to have some of the odder bits edited out. The Chinese version, for example, has a longer, and stranger and more fun, version of the musical scene in front of the bun shop.

I didn't get much done at work today. I'd like it chalk it up to the cold I'm not quite recovered from, but it's probably just me.

Then I tried to upgrade drupal at night. It was much more of a pain than it should have been, but I managed to get it up to something that supposedly has known security problems fixed. When it first failed I was saved by the last resort of restoring (with just cp -a) the contents of /var/lib/mysql from a backup. Hope that doesn't screw up anything too badly....

I went back to work today, though really not for much more than half a day.

On the way in, I traded in for some new comic books at the media union.

I've also started Kazuo Ishiguro's "Never Let Me Go". As usual the narrator is unreliable, and the important information never seems to be where they tell you it is. In this case the book seems to have some kind of dystopian science-fictional premise which is being revealed as slowly as possible. It's very creepy, and the idea of eventually discovering what's actually going on fills me with dread in the way that Lovecraft stories are supposed to but never manage to.