disk-access

问题 Is VARCHAR(100) any better than VARCHAR(500) from a performance point of view? What about disk usage? Talking about PostgreSQL today, not some database some time in history. 回答1: They are identical. From the PostgreSQL documentation: http://www.postgresql.org/docs/8.3/static/datatype-character.html Tip: There are no performance differences between these three types, apart from increased storage size when using the blank-padded type, and a few extra cycles to check the length when storing into

问题 I am learning OS development and I'm in preliminary level. I created a simple boot loader. To access other files on the disk(say HDD or USB drive), which addressing mode should I use?(CHS or LBA or INT 13h extensions). Which of these addressing mode is very efficient(means, can be used for most of the drive)? Thanks 回答1: First of all, the INT13h extensions are an extension to an API, not an HD addressing method. You have to settle on whether you are going to use the BIOS or direct hardware