問57
頻出度★★☆
フラッシュメモリを用いた SSD (Solid State Drive) は, ハードディスクの代わりとして期待されている記憶装置である。この SSD を用いるときに留意すべき点はどれか。
平成21年度 秋期 ITパスポート試験 問57
テクノロジ系コンピュータ構成要素 › メモリ
This question's explanation and your answers so far.
解説
問 57
- ア
正解 ア is correct. Flash memory, the storage medium of an SSD, holds data in cells where charge is enclosed by an insulating film, and this film degrades a little each time writing and erasing are repeated. For this reason each cell (block) has an upper limit on how many times it can be rewritten, and a block that exceeds the limit can no longer hold data correctly. SSDs extend their life with techniques such as wear leveling (control that spreads write locations out), but the fact that a limit exists does not change, so for uses with frequent writing the lifetime must be kept in mind.
Incorrectイ
This is the opposite. In flash memory, reading is the fastest, while writing (especially rewriting that involves erasing) is slower. The statement that reading is slower than writing does not match the characteristics of an SSD.
Incorrectウ
It is the hard disk, which spins magnetic disks and reads and writes with a magnetic head, that is weak against vibration and shock. An SSD is a semiconductor storage device with no moving parts, so its shock resistance is in fact higher than that of a hard disk, and this is not a point to keep in mind.
Incorrectエ
Marked performance degradation due to fragmentation is a characteristic of the hard disk, because the head movement (seek) time increases. An SSD can access any location in roughly the same time, so the performance drop from fragmentation is small, and this too cannot be called a point specific to SSDs.
ここがポイント
- An SSD is a semiconductor storage device using flash memory; it has no moving parts, so it has high shock resistance, and its speed hardly differs by access location (the effect of fragmentation is small).
- Flash memory cells degrade with each rewrite, so the number of writes has an upper limit; this is the biggest point to keep in mind with an SSD. Wear leveling spreads writes out to extend the lifetime.
用語