Operating Systems Lecture Notes

25 January 2012 • Pop Quiz

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A Quote

This command sends 16,384 16KB blocks of null bytes, creating a file with a total size of 16,000 bytes × 16,384/1024 kilobytes = 256 kilobytes or 256MB. Write the time down. Then calculate the time of reading, sending the file to /dev/null:

time dd if=/home/tempo of=/dev/null bs=16k

Olexiy Tykhomyrov and Denis Tonkonog
Starting Share Files with NFS
Linux Journal, January 2002

• What's wrong with this quote?

The Problems

This command sends 16,384 16KB blocks of null bytes, creating a file with a total size of 16,000 bytes × 16,384/1024 kilobytes = 256 kilobytes or 256MB.

• 256 kilobytes ≠ 256MB.
• 16,384 is the number of 16 KB blocks, it should not be divided by 1024.
• You could also argue that 16KB ≠ 16,000.
• 16,000 byte/block × 16,384 blocks = 256MB.

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This page last modified on 2012 January 25.