On Wednesday 02 March 2005 21:15, ALeine wrote:
> phk@phk.freebsd.dk wrote:
> > I gave up on journalling myself because IMO it complicates
> > things a lot and the problem it solves is very very small.
>
> If only hardware manufacturers were to equip hard drives with
> a mechanism to ensure atomic writes. A capacitor large enough
> to hold enough energy to flush the cache upon detecting the
> power supply was cut would be sufficient.

This has come up many times.  In reality, no, that's nowhere near sufficient, 
because you might have to employ error correction during the write.  In 
addition, in modern disks, the emphasis at power loss is on getting the heads 
off the disk as fast as possible -- if you don't, the disk is dead -- so any 
power available is devoted to that.