問81
頻出度★☆☆
A 社は業務で使用しているサーバのデータをサーバのハードウェア障害に備えてバックアップをしたいと考えている。次のバックアップ要件を満たす計画のうち，A 社のバックアップ計画として適切なものはどれか。 〔バックアップ要件〕 ・サーバ障害時には障害が発生した前日の業務終了後の状態に復旧したい。 ・業務で日々更新するデータは全体に比べてごく少量だが，保有しているデータ量が多く，フルバックアップには時間が掛かるので，月曜日～土曜日にはフルバックアップを取ることができない。
平成24年度 春期 ITパスポート試験 問81
テクノロジ系ソフトウェア › ファイルシステム
This question's explanation and your answers so far.
解説
問 81
Incorrectア
The storage location (output to external media and stored) is appropriate, but no backup is taken from Monday to Saturday. Recovery is therefore possible only up to the state of the previous Sunday; for example, if a failure occurs on Thursday, the first requirement — restoring to the state as of the end of business on the previous day (Wednesday) — cannot be met.
Incorrectイ
As with ア, no backup is taken from Monday to Saturday, so the state of the previous day cannot be restored; in addition, the backup files are placed in a folder inside the server. Since what is being prepared for is a server hardware failure, if the machine itself breaks down the backup files are lost along with it, so this choice is inappropriate on two counts.
- ウ
正解 There are two requirements, and the premise also states that the backup is taken to prepare for server hardware failure. Choice ウ satisfies all three of these points. (1) A full backup is taken on Sunday, and from Monday to Saturday a differential backup of the data updated, added, or deleted since the full backup is taken every day, so the state as of the end of business on the day before the failure can be restored from the Sunday full backup plus the previous day's differential backup. (2) On weekdays only the changed portion is backed up, and the data updated daily is very small compared to the whole, so there is no need to take a time-consuming full backup from Monday to Saturday, which meets the requirement. (3) Because the backup files are output to external media and stored in a designated location, the backups are unharmed even if the server hardware fails, so recovery is certain.
Incorrectエ
The backup method (a full backup on Sunday plus differential backups on weekdays) is appropriate, and restoring to the previous day's state is possible. However, the backup files are stored in a folder inside the same server as the backup source, so when a hardware failure occurs the backup is lost together with the data itself and recovery is impossible in the first place. As a rule, backups should be kept on media and in a location separate from the original data.
ここがポイント
- A differential backup collects, in one go, all the data that has changed since the most recent full backup. It takes little time each day, and recovery needs only one full backup plus one differential backup for the day you want to restore to. It is the standard combination when a full backup cannot be taken every day.
- A backup meant to prepare for hardware failure should be output to external media that the failure cannot reach, and stored in a designated location. If it is kept inside the same server as the backup source, the backup is lost at the same time the machine fails, which defeats its purpose.
用語