On all Linux distros currently available, the sysctl variables vm.dirty_background_ratio and vm.dirty_ratio are set to 5 and 10 respectively, or thereabouts. These variables indicate the amount of RAM that can be occupied by stuff that needs writing to the disk, before said stuff must be flushed - asyncronously for dirty_background_ratio, synchronously for dirty_ratio. Mind, those defaults are for when your computer is plugged in. For laptops on battery power, those variables are set by pm-utils to 40 and 60. My question is, why on Earth would anyone set them so high? If you have 1+ GB of RAM, then when you hit that 5% limit, your laptop or desktop computer will freeze up. Decompress a big tarball? Copy a few GB from an external drive? Bam, freeze. I don't even want to think about what would happen with dirty_background_ratio at 40%. Sure, increasing dirty_background_ratio will delay the write, but eventually it will have to happen, and when it does, watch out. (Also, there's the obvious risk of data loss when significantly delaying writes...) In my experience the default settings tend to result in huge slowdowns when e.g. installing stuff, whereas vm.dirty_background_ratio=1 and vm.dirty_ratio=2 result in much more reasonable desktop performance, and only a small decrease in throughput. So... Whence the defaults?