Quiz 5: Data Storage Technology

Computing

Magnetic Disk Drive a) The formulae to calculate drive capacity is given below: img Number of img Number of img Tracks per img Sectors per img Let us assume the Sector img img b) To maximal read efficiency, assume data are organized. So, the read will occur cylinder by cylinder. This will result in 1024 TTT (Track-to-track) seeks. img and 10 HTH(Head-to-Head) switches per track per second img img 0 img 1 Time required to read the tracks (exclusive of seeks and switches) img 2 There is no rotational delay when reading sequentially img 3 c) Time required for serial access time. It is used to read the second of two sequential sectors If the sectors lie on the track and same platter then Sequential Access Time is rotation speed. There are 50 sectors per track. img 4 img 5 To the fraction of sequential reads accounts by using Average serial access time that will require a HTH switch (one every 50 sectors) and a TTT seek (1 every 500 sectors). To compute this adjusted access time, divide the time required to read the entire disk by the number of sectors. img 6 d) Each read requires half of the rotation delay, seek over 512 tracks, switching through 5 heads, and img 7 of a rotation to read the data. img 8 , A seek over 512 tracks requires img 9 Switching through 5 heads requires img 0 Reading the information requires 0.00012 seconds. Average access time is the sum of all these values img 1

Memory expansion in computers Three types of computer selected are: personal computers, workstations, and servers. The table showing prices for expansion of RAM in different computers is given below: img Factors responsible for variation in memory price for each computer: • Size: The price of memory depends on the size of RAM, bigger the size, more is the price of memory. Cost of expansion of 4 GB memory is more than that of 2 GB memory. • Speed: If the data transfer rates of RAM is faster, the cost of RAM is more. High speed RAM is costlier than the low speed RAM. • Technology: The price of RAM depends on the type of technology used in its manufacture. Latest technology RAM will cost more than the outdated technology. For example, DDR3 is cheaper than DDR5.

Speed of an electrically based processing device The following factors limit the speed of an electrically based processing device: • Data Transfer Rate : This rate is computed by dividing 1 to the access time expressed in seconds and then multiplying the result by the unit of data transfer rate which is expressed in bytes. If the data transfer rate is high then the speed of the electrical device must be higher. • Access Time : Access time is the time required to perform one read or write operation on the storage device. • Size of a Block : A block is the unit of secondary storage data transfer. It is normally stated in bytes and varies widely between various data storage device. The size of the block also limits the speed of the electronic device many times. • Number of Registers : Registers in the CPU are the storage locations for data and instructions and CPU have limited number of registers. These registers also decide the speed of the electronic device.