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Chapter 13: Problem 3

Define the following terms: disk, disk pack, track, block, cylinder, sector, interblock gap, read/write head.

Short Answer

Expert verified
These terms are fundamental to understanding disk-based storage systems. They include components of the system (like the read/write heads and the physical disk itself), how data is organized and stored (tracks, sectors, and blocks), and other concepts relevant to the physical workings and limitations of such systems (like cylinders and interblock gaps).

Step by step solution

01

Define Disk

A disk, also known as a disc in some uses, is a data storage device that uses magnetic storage or optical storage technologies to store and retrieve digital data.
02

Define Disk Pack

A disk pack is a stack or collection of hard disk platters, each capable of recording on both surfaces.
03

Define Track

A track is a narrow recording band that forms a full circle on the surface of a disk. Data is stored and read back in these tracks.
04

Define Block

A block, also known as a physical record, is a sequence of bytes or bits, usually containing some whole number of records, that has a maximum length, the block size.
05

Define Cylinder

A cylinder is a set of tracks on a multi-platter drive that exist in the same relative position to one another. All surfaces contain tracks, thus when read or write heads move to a given track, a grouping of tracks, all at the same position, is available for reading or writing. This group is called a cylinder.
06

Define Sector

A sector is a sub-division of a track on a magnetic disk or optical disc. Each sector stores a fixed amount of user-accessible data, traditionally 512 bytes for hard disk drives (HDDs).
07

Define Interblock Gap

The Interblock gap is the empty space left between data blocks on magnetic tape or hard disk sectors to allow for read/write head movement and speed changes.
08

Define Read/Write Head

The read/write head is the mechanism in a hard drive or floppy disk drive that reads and writes the data onto the storage medium.

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Most popular questions from this chapter

Suppose we want to create a linear hash file with a file load factor of 0.7 and a block. ing factor of 20 records per bucket, which is to contain 112,000 records initially. a. How many buckets should we allocate in the primary area? b. What should be the number of bits used for bucket addresses?

Suppose that a file initially contains \(r=120,000\) records of \(R=200\) bytes each in an unsorted (heap) file. The block size \(B=2400\) bytes, the average seek time \(s=\) \(16 \mathrm{ms}\), the average rotational latency \(r d=8.3 \mathrm{ms}\) and the block transfer time \(b t t=\) \(0.8 \mathrm{ms} .\) Assume that 1 record is deleted for every 2 records added until the total number of active records is 240,000 a. How many block transfers are needed to reorganize the file? b. How long does it take to find a record right before reorganization? c. How long does it take to find a record right after reorganization?

Write pseudocode for the insertion algorithms for linear hashing and for extendible hashing.

Describe the mismatch between processor and disk technologies.

Suppose that a disk unit has the following parameters: seek time \(s=20\) msec; rota tional delay \(r d=10 \mathrm{msec} ;\) block transfer time \(b t t=1 \mathrm{msec} ;\) block size \(B=2400\) bytes; interblock gap size \(G=600\) bytes. An EMPLOYEE file has the following fields: \(\mathrm{SSN}, 9\) bytes; LASTNAME, 20 bytes; fIRSTNAYE, 20 bytes; MIDOLE INIT\(, 1\) byte; BIRTHOATE, 10 bytes; ADDRESS, 35 bytes; PHONE, 12 bytes; SUPERVISORSSN, 9 bytes; DEPARTMENT, 4 bytes; JOBCODE, 4 bytes; deletion marker, 1 byte. The EMPLOYEE file has \(r=30,000\) records, fixed-length format, and unspanned blocking. Write appropriate formulas and cal. culate the following values for the above eMPLoyee file: a. The record size \(R\) (including the deletion marker), the blocking factor \(b f r,\) and the number of disk blocks \(b\) b. Calculate the wasted space in each disk block because of the unspanned orga nization. c. Calculate the transfer rate \(t r\) and the bulk transfer rate brr for this disk unit (see Appendix B for definitions of tr and btr). d. Calculate the average number of block accesses needed to search for an arbitrary record in the file, using linear search. e. Calculate in msec the average time needed to search for an arbitrary record in the file, using linear search, if the file blocks are stored on consecutive disk blocks and double buffering is used. f. Calculate in msec the average time needed to search for an arbitrary record in the file, using linear search, if the file blocks are not stored on consecutive disk blocks. g. Assume that the records are ordered via some key field. Calculate the average number of block accesses and the average time needed to search for an arbitrary record in the file, using binary search.
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