ITPEC IP April 2021 Question 23

Stored data cannot be read quickly — fragmentation scatters a file across the disk and slows reading.

When files are written and deleted again and again, the free space breaks into small gaps, and a new or growing file is split over several non-consecutive areas (fragmentation). The file system records where every piece is, so the data is still written and read correctly. But on a hard disk the head must seek from piece to piece, so reading a file takes longer. Defragmentation rearranges the pieces into consecutive areas and restores the speed.

Answer (d)

Why not others:

• •(a) — where a file's blocks lie on the disk has no effect on whether antivirus software detects a virus
• •(b) — the file system writes into scattered free areas and keeps track of them, so writes are still correct
• •(c) — the pieces are read back in the recorded order, so the data is correct, only slower to fetch

Key rule: Fragmentation costs speed, not correctness; defragmentation is the remedy, and it matters for hard disks with moving heads rather than SSDs.

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