OS drives come in a variety of speeds. Currently following drives are to be considered in following order:

• SSD SLC ( = very expensive)
• SSD MLC
• USB thumb drive
• harddrive
• SD card

Come in the following form factors:

1- SSD over mini-PCIE connection. (A regular PCIE is better, but not supported for netbooks)
2- SSD over Sata
3- SSD over PATA
4- external SSD's via USB connection cable

SLC SSD drives are mainly used in the industry,due to being very expensive. They have high IOPS, even if their continuous write and read speeds are not that exceptionally high!
MLC drives are more affordable, and the best suited as replacement drive for a harddrive.
Currently (2009) Intel has the upper hand on SSD drives.
SSD's over SATA are common and ok. PATA harddrives are considerably slower, and have about the same bus speed as esata drives.
External drives over USB should be avoided, though they can still be faster than USB memory sticks.

Come in a variety of choices too, and are to be considered in following order:

• Combined eSata-USB stick (one side USB 2, the other eSata)
• Performance USB flash drives
• Vista readyboost ready USB sticks
• Your regular walmart/supermarket/photostore flash drives.

The latest gen of usb flash drives support both an esata and a USB2 connection. They are considered the fastest,next to perhaps upcoming USB3.0 flash drives that are only in the making at this moment.
Performance USB flash drives are generally focused on high continuous writes. Their IOPS might be low, but they try to improve IOPS by improving overall continuous read or write speed of the drive.
Vista ready boost ready dives was an older protocol for USB drives with faster than 10MB/s read and write. Current esata+USB drives reach about 50MB/s over esata,and 30MB over USB2.0.
Regular USB drives that are cheap and found in stores still have low iops,and low continuous transfer speeds.
Though they can host an OS, they most likely are going to be responsible for short system freezes, hickups and small hangs.

Are third on the list. Regular harddrives are way slower than USB flash drives for running OS drives,and they use more battery too.
They do have greater capacities though.

Should not be used for OS, (or at least are not recommended) due to their low ECC (Error Correction Code).
But if you would use an SD card, use an SDHC Class 6 card!

• JKK's netbook blog
• Runcore netbook SSD replacements
• Conics SSD replacement page

                                                                     Last Page Update: 03.dec.2009