Ubuntu Full install | Ubuntu full install 2 | Ubuntu install to SD Card | Simple install via USB
The Asus eee 901 is shipped with either windows xp or a lite linux Xandros system, however if you want to install ubuntu without removing the original operating system then an option would be to install and run ubuntu from an SD card.
The installation process is the same as the other guide but with the difference of selecting the SD drive as the installation destination rather than the built in SSD disk.The installation process does take quite a bit longer than when installing to the main drive so be patient!
Once installed, you simply need to change the boot configuration in the bios to allow the eee to boot up ubuntu. The OS takes up about 2.7Gb of disk space with the rest being allocated to the /home directory so a 4gb or 8gb sd card would do the job.
The fasted type of SD card is a 'class 6' disk and is strongly recommended if you want to try this type of install. Once complete there is a noticeable decrease in overall performance when operating from the SD card, however this is only slight and doesn't impair the overall feel and function of the 901. You may want to try setting up a swap file to see if that helps with performance, as the card can be replaced its not so crucial as using the main drive which of course cant be replaced.
I would suggest sticking with a well known brand of SD card and be aware of the fakes that are floating about on ebay, Sandisk, Crucial, Kingston are all a good choice.
Of course if you had a reaon or need for running multiple operating systems you could also use this method for Vista, XP, other linux distro's etc and have a collection of cards with differing OS's on them.