0623のHW

1.Imagine that the bitmap showing which disk blocks are free has become unreliable, so you decide to rebuild it by walking through all of the in-use inodes. Assume on-disk inodes are 128 bytes, and the file system was initialized to hold a maximum of one million files. Your disk has a transfer rate of 40 megabytes/second, and can execute a random operation in 10milliseconds. It holds 100GB.

A.If all of the inodes are stored in one contiguous chunk of disk, how long will it take to read them all?

128 * 1000000 = 128MByte
128 / 40 = 3.2 sec


B.If 100,000 of the files each use a single indirect block that is randomly placed on the disk, how long will it take to work through all of them?

100000 * 10
= 1000000 msec
= 1000 sec

C.Using the same type of disk, how long would it take to read every 4KB block on the disk in random order?
100GB / 4KB = 25000000
25000000 * 10 msec = 250000 sec

2. Do you back up the data on your computer? If so, how?
A. Execute a data backup. This backup may be of any type, using any tool, and may be just your user files or may be the entire system. You may back up to CD/DVD, external disk, tape, or over the network to a server.
scpを用いてネットワーク上のサーバへsystem()を使用して、backupを取る。
systemでscpを実行し0 byteのファイルを転送したときの時間は、10回平均で0.5936 sec
iperfで測定した通信速度は15.2Mbps

B.Report how long it took to perform your backup, and how much data was transferred.
1Gのファイルを転送する。
かかった時間は581.6871 - 0.5936 = 581.0945 sec