Question

I was asked in the interview regarding O.S

we make virtual memory out of hard disk than why is accesing swap faster than accessing hard disk.

Please help me understanding the concept.Or else redirect me to the proper forum.

Answer 1

• First, as @Celada said, there’s chances your data will in memory (has not been swaped out) when you map your file to memory or put your data in memory. This may be faster than you directly access your file or your data.
• Second, OSes have very efficient swap algorithm that probably better than yours. So for example, if you need to read a very large file(maybe 2GB large or more), you need to do kind of swapping yourself and probably much slower than using OS swap.
• Third, in practice, system administrators usually put /swap in a separate partitions or even separate disk or even faster device, so you can take advantage of it.