增量备份与差异备份的区别（Incremental vs. differential backup: A comparison）

译自http://www.computerweekly.com/news/1347703/Incremental-vs-differential-backup-A-comparison

Differential backup -- 差异备份

Differential backups copy those files that have been changed since the last full backup took place. So if a full backup was done on Day 1, Day 2's differential will copy all of the files that have changed since Day 1's backup copied everything. Day 3's differential backup will also copy all of the files that have changed since Day 1's full copy was made.
差异备份拷贝那些自上一次完全备份后发生改变的文件，所以如果第一天做了完全备份，第二天的差异备份将会拷贝那些第一天完全备份后发生改变的文件，第三天的差异备份同样会拷贝那些第一天完全备份后发生改变的文件。

The key advantage of differential backups comes when data needs to be restored. Because a full backup was taken and the differentials copied everything that subsequently changed, only the full backup and the latest differential need to be restored.
差异备份的优势是当数据需要还原时，因为已经做了完全备份和之后的改变，只需要完全备份及最新的差异备份即可去做还原。

The main disadvantage is that the size of the differential copy increases each time a backup is taken until the next full version is made, which can begin to impinge on backup window duration.
差异备份的缺点是备份文件的大小会随着备份次数的增加而增加，直到下一次完全备份。


Incremental backup -- 增量备份

Incremental backups copy all of the files that have changed since the last backup was made. They do this whether the last backup was a full one or an incremental copy. So if a full backup was done on Day 1, Day 2's incremental will back up all of the files that have changed since Day 1. Likewise, Day 3's incremental backup will only copy those files that have changed since Day 2's incremental took place.

增量备份拷贝上一次备份结束（完全备份、增量备份、差异备份）后发生改变的文件，而和上一次是否为完全备份或增量备份无关。所以如果第一天做了完全备份，第二天的增量备份将会备份那些第一天后发生改变的文件，第三天的增量备份将拷贝第二天备份后发生改变的文件。

The main advantage to incremental backups is that fewer files are copied in the period between full backups, which means you will get a shorter backup window. The main disadvantage is that when you want to carry out a complete restore, the most recent full backup and all of the subsequent incremental copies must be restored. This can make the restore process a lengthier one than when using a full backup plus the most recent differential copies only.

增量备份的优点是在完全备份中间拷贝更少的文件，这意味着你将得到较短的备份窗口。其主要缺点是如果你要执行完全还原，最近的完全备份及所有的增量备份必须被还原，这样比差异备份还原过程更长一些。

Incremental vs. differential backup: A comparison