# External Sorting - Calculate passes with different number of disks

Let suppose that we have a file with n = 10^6 records. The block size is B = 10 records and we have available main memory m = 20 blocks. (Sorting with MergeSort)

a) If we have 1 disk find minimum available to sort file in 2 passes b) If we have 2 disks how many passes we need to sort the file completely

I have started to read about external sorting and i am confused about how to answer this questions. I don't know how to think about to solve it.

I read the solution of this exercise 1 which is in the textbook that i read https://www2.cs.duke.edu/courses/spring03/cps216/lectures/rec-03-quiz.pdf

and i am confused about the connection of terms in 2 exercises. So i need some help to solve the questions that are solved in the link-file but with my data.

• Welcome to COMPUTER SCIENCE @SE. Please turn into a block quote the part that quotes a problem you have been faced with (rather than you want to present here for others to sharpen their wits). If at all possible, identify the source and credit the originator - hyperlink welcome. – greybeard Nov 24 '20 at 5:06
• I find the question quoted lacking. What capabilities am I supposed to assume in a "disk"? "Tapes" used to be much more distinctive: single access point per drive, and positioning wasn't orders of magnitude faster than transfer. (I was surprised to "find" HDD capacity shipped currently surpasses that of SSDs by about as much as number of SSD units shipped surpasses that of HDDs.) – greybeard Nov 24 '20 at 5:14
• Professor should start with “I have a seven port USB hub with seven 5TB spinning hard drives plugged in. I also have a 256GB SSD drive. ...”. – gnasher729 Nov 24 '20 at 10:55
• I have updated the post with a similar practise problem that i have read and also explain which is my problem. – Maria Zak Nov 24 '20 at 17:54