How can I measure that I have to change my disk or add before damaged .

[Vahric MUHTARYAN]

Hi , 

	İn Windows I can watch my disks which I have to add disk because it
takes too much I/O wait . I know I can watch it via vmstats but in Windows I
have a some value and when machine pass this value frequency I know that I
have to make some thing maybe increase the disk or I can find out one disk
will be damaged in short time ?  

	Does anybody have knowledge about this ?!  


Vahric MUHTARYAN