Yet another Pop Quiz COSC 6360 Fall 2015

The rules On any sheet of paper, please write  You full name, first name first  Today's date  Your answers to the five true or false questions on a single line as: TTTFT  You can erase or overwrite previous answers but your final answer should contain no corrections

T/F questions on log-structured file systems (LFS) FFS and other non log-structured file systems maintain no i-node map. LFS maintains its i-node map at a fixed location. When a computer is shut down properly, all the information required to access its LFS can be found at the last file checkpoint. A LFS will recover faster from a system crash than a conventional file system. When a LFS has to make space, it should clean up first disk segments that were recently used.

Answers FFS and other non log-structured file systems maintain no i-node map. LFS maintains its i-node map at a fixed location. When a computer is shut down properly, all the information required to access its LFS can be found at the last file checkpoint. A LFS will recover faster from a system crash than a conventional file system. When a LFS has to make space, it should clean up first disk segments that were recently used.

T/F questions on RAID If the mean time to failure of an individual disk is 100,000 hours then the mean time to failure of an 100-disk array is 1,000 hours The space overhead of a RAID level 5 array with ten disks is 20 percent. The minimum cost of a single block update in a RAID level 5 array is one read and two writes RAID level 6 arrays protect their data against all triple disk failures within the array RAID level 5 uses an omission correction code.

The answers If the mean time to failure of an individual disk is 100,000 hours then the mean time to failure of a one hundred disk array is 1,000 hours. The space overhead of a RAID level 5 array with ten disks is 20 percent. The minimum cost of a single block update in a RAID level 5 array is one read and two writes. RAID level 6 arrays protect their data against all triple disk failures within the array. RAID level 5 uses an omission correction code. TFTFT

T/F questions on Video Streaming BitTorrent ensures that all peers receive the contents of the files they download in sequence The best chunk selection policy for video streaming is selecting the rarest chunk(s) within the current sliding window. Larger sliding windows imply a longer wait for the service users When a new user starts streaming a file, it has nothing to offer to other peers P2P solutions cannot handle flash crowds

The answers BitTorrent ensures that all peers receive the contents of the files they download in sequence The best chunk selection policy for video streaming is selecting the rarest chunk(s) within the current sliding window. Larger sliding windows imply a longer wait for the service users When a new user starts streaming a file, it has nothing to offer to other peers P2P solutions cannot handle flash crowds FTTTF

T/F questions about SSH SSH uses secret key/public key for encrypting all communications between users and servers. SSH servers have two secret key/public key pairs. One of these keys changes every week. SSH offers no way to authenticate a server the first time you connect to it. SHA stands for Secure Hash Algorithm

The answers SSH uses secret key/public key for encrypting all communications between users and servers. SSH servers have two secret key/public key pairs. One of these keys changes every week. SSH offers no way to authenticate a server the first time you connect to it. SHA stands for Secure Hash Algorithm. FTFTT