How to improve harddisk performance
This tweak can increase the performance of your HDD by enabling DMA, IDE 32-bit I/O and setting the interrupt-unmask flag, which improves Linux's responsiveness. The last parameter sets the IDE Block Mode to fetch 16 blocks per I/O interrupt. Depending on your drive this value may vary (run hdparm -iI /dev/hda to find it out).
Caution: On some hard disks, inadvertent experimenting with hdparm options may corrupt the filesystem! Again, have a look into the man page of hdparm to find out if your model is affected.
On systems where the traditional ATA/(E)IDE and ATAPI stack is used, the following is appropriate:
hdparm -d1 -c1 -u1 -m16 /dev/hda
On newer systems with SATA hard drives (exposed e.g. as /dev/sda), only -d option is applicable, and it has no effect as DMA is already enabled. (An R61, interestingly, has a SATA HDD whilst the CD+DVD drive is connected via an IDE controller.)
You may also want to tune the acoustic setting (-M), power management mode (-B): for best performance, try -M254 and -B254).
Successfully tested Thinkpad models
The settings above have been successfully tested on the following models:
T20, T22, T23, T40
Please add your model if missing.