Graham Stoney wrote:
> Paul Moody's mini-HOWTO on Embedded Linux at:
> http://users.bigpond.com/paulmoody/Mhow11c.html
> gives one approach to using a Flash memory drive with Linux, by loading the
> contents into a ramdisk at boot time.
>
> RAM is cheaper than Flash, so for the most part this makes sense. However, if
> you're stuck with less RAM than Flash, or if you're using a real hard drive,
> it may make more sense to mount the root filesystem from the drive read-only.
>
Hmmmmmmmmmm yes there are a myriad of configurations that can be implemented to
produce a more robust system design and though the idea of a read only harddrive
approach has merit in preventing corruption of filesystems during power failures
or accidental erasures it was not the sole benefit to be obtained from a ramdisk
/ flash system.
Briefly my design goals as follows ...
No Mechanical parts - 1000 G rating ( vibration ).
Small - It all fits on one card
Low power - No fans at all in our micro servers. ( 5 - 8 watts total )
Filesystem cannot be ( permanently ) corrupted ( its all in RAM )
If critical processes / file CRC failure watchdog reboots.
Largish capacitor on power supply keeps system up for 500 ms ... time
enough to save critical data to flash.
Flash can be reformatted / reloaded totally ( hoping power does not fail
:-) )
Flash can be removed whilst system up ( again hoping :-) )
Flash a darn sight more convenient ( we use flash cards )
File read / writes ( being ram based ) are ultra fast.
These are just for the micro server itself ... there are additional benefits to
be had when implemented in a large system such as network management (
telecommunications ) which is my field.
Regards to all.
Paul Moody.
