Sometimes you're the windshield, sometimes you're the bug

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Pardon me while I indulge in some geek talk. So I'd been needing a couple of much larger external hard drives for some time, one to hold the music collection that had long since overspilled the Maxtor 200 Gb drive, and one to backup the entire system. After some hunting around, I found a great price on a couple of Seagate FreeAgent Pro FireWire drives, one 500 Gb and the other 750 Gb:

A terabyte and a quarter
Looks good in the light...

A terabyte and a quarter in the dark
...looks even better in the dark!

That's a terabyte and a quarter! Right there on my desk!

Anyway, these babies were easy to install and get running, and it was almost as easy configuring the autobackup software to start saving everything to the huger drive. I moved a lot of files around, and everything was cool.

But then a few days ago I began to notice an annoying bug in the personal music server I wrote for myself a few years back (now serving 49,428 tracks!). My music would play fine, but the component that tallies what I've played (and also allows me to resume an album or playlist later where I left off, and to chain play actions together) began failing at what seemed to be random times.

Looking at the code, I figured that maybe the database had gotten big enough that certain queries weren't executing quickly enough, so I rewrote those bits. I thought I had fixed the problem, but then the failures started happening again. So I inserted some debugging code and was able to discover that from time to time database writes were simply being ignored, though reads continued to work fine. I was completely flummoxed.

But this morning I had the Eureka! moment. It was the new autobackup software! It runs constantly in the background, monitoring files that change and then duplicating them to the backup drive during off moments. Unfortunately, though, the database file changes every few minutes while I'm playing music, so it's always being backed up. If a copy operation is executing (and that takes a few seconds, since it's an 80 Mb file), then the file is locked and my music server can't write to it.

In fact, this explains some transient errors I've seen in other applications.

Anyway, I've taken the database out of the backup lineup for the moment, but I'm going to have to really dig into this software and see how finely I can control the backups. I will be annoyed if I can't control when the autobackups occur.

On the plus side, though ... a terabyte and a quarter! Right there on my desk!

[ original post:  http://shunn.livejournal.com/421420.html ]

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This page contains a single entry by William Shunn published on September 25, 2007 10:00 AM.

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