If memory
must be copied to or from disk because there is more requested than can be
satisfied, what’s the penalty for doing this?
•
Memory
vs. disk speed is…?
A)
Memory is 100x faster than disk
B)
Memory is 1,000x faster than disk
C)
Memory is 10,000x faster than disk
D)
Memory is 100,000x faster than disk
E)
Memory is 1,000,000x faster than disk
F)
I have no memory of the event, your honour
A modern disk
will respond to an I/O in about 5 milliseconds (5 * 1/1000 of a second). Access to memory is usually in the order of
50 nanoseconds (50 *1/1,000,000,000 of a second).
That makes
disk access a hundred thousand (100,000) times SLOWER than memory access. Tiny
numbers like this are difficult to comprehend, so imagine that the memory
access time was 1 second. To write
something to disk would then take about 27 ¾ hours to complete.
That’s one
good reason for avoiding swapping if at all possible! On Monday I'll be looking at vKernel Swap.
In the meantime why not take a look at some of our VMware on-demand webinars and white papers. Join our Community via our Resources section and get free access.
Phil Bell
Consultant
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