June 2007 Archives
June 17, 2007

Second autocross


Yesterday was another miserably cold day at Marina. While in Bay Area temperatures finally dropped from the high 90s into low 70s, Marina saw a lot of fog, wind and cold weather. The autocross at Marina was nevertheless very rewarding, this time with a very interesting and challenging course. I ended up 5th in my car's class. While the result was pretty good, I could have done a lot better.

The most challenging part is recognizing the mistakes you make and try to avoid them in a consistent manner. This is easier said than done, as the course's features come at you very fast, and a mistake in a turn happens usually because of another one few turns before. So concentration is key, as well as a good understanding of what your car can do. I still have a lot to learn, but it's fun.

Posted by ovidiu at 06:44 PM | Comments (0) |
June 07, 2007

MacPro disk access performance (take 2)


In a previous weblog entry I measured the disk access performance on MacPro. Few days ago I decided to change my two 750GB drives configuration from RAID 1 (mirrored mode) to RAID 0 (stripped mode).

I backed up the RAID disk on an external drive and I recreated the RAID setup. To destroy the old RAID disk I had to boot the machine in safe mode (hold down the "Shift" key during computer boot-up). Otherwise DiskUtil would not be able to unmount the drive. After creating the RAID 0 disk, I restored the disk from the backup.

I ran the same commands as I did few months ago:

$ time dd if=/dev/zero of=<file> bs=1024 count=1048576

$ time cat <file> | wc -c

One thing I did notice is that running the cat to /dev/null (as I did in the previous entry) yields a really low number on MacOS X 10.4.9. This indicates a possible optimization in the operating system. I changed the command to count the number of bytes using wc. This adds a negligible CPU load, and probably some inefficiencies in how the stdin data is read by wc, but overall should not influence much the result. Here are the results combined with those from the last run:

DriveRead time (seconds)Write time (seconds)
internal 160GB14.9014.64
internal, software RAID 0, 1.5TB7.6810.65
internal, software RAID 1, 750GB18.0521.94
external, hardware RAID, USB2, 400GB49.4357.30

So clearly setting up a RAID 0 disk improves the performance of your disk! In real life Adobe Lightroom takes a lot less time to start up than before. Other applications may benefit as well from this, but it's too early to tell. My previous recommendation remains: use an external USB or Firewire drive for backups only, and optimize the internal disk system for performance.

Posted by ovidiu at 10:15 AM | Comments (3) |
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