Time Machine是macOS中的標準備份軟件應用程序。Time Machine進行過去24小時的每小時備份，過去一個月的每日備份以及超過一個月的所有內容的每周備份。它會進行備份，直到卷空間不足為止。通常，這些備份存儲在具有HFS +文件系統(tǒng)的磁盤上。

Time Machine?is the standard backup software application in macOS. Time Machine makes hourly backups of the last 24 hours, daily backups for the past month, and weekly backups for everything older than a month. It makes backups until the volume runs out of space. Often these backups are stored on a disk with HFS+ file system.

在本文中，我們將討論Time Machine中數(shù)據(jù)存儲的詳細信息以及如何在數(shù)據(jù)恢復過程中使用它。
In this article, we will discuss the details of data storage in the Time Machine and how to use it in the data recovery process.

HFS+中的硬鏈接 Hard links in HFS+

Time Machine使用硬鏈接存儲數(shù)據(jù)。硬鏈接是將同一文件放置在不同文件夾（目錄）中的一種方法。
Time Machine uses Hard links to store data. Hard links are a way to place the same file in different folders (catalogs).

讓我們舉個例子。有兩個文件：
Let’s take an example. There are two files:

\folder1\file1.txt

\folder2\file2.txt

一個文件是另一個的硬鏈接。這意味著：
And one file is the hard link of another. It means that:

• 操作系統(tǒng)和大多數(shù)軟件都將這兩個文件識別為單獨的文件；
  both files are recognized as separate files by the operating system and most software;
• 如果我們更改一個文件的內容，則另一個文件的內容會自動更改；
  if we change the content of one file, the content of another file is changed automatically;
• 如果我們刪除一個文件，則另一個文件保持不變
  if we delete one file, another file remains intact

可以為一個文件創(chuàng)建多個硬鏈接，也可以為目錄創(chuàng)建硬鏈接。
It’s possible to create several hard links for one file, it’s also possible to create a hard link for catalogs.

對于HFS +文件系統(tǒng)，有一個原始文件，并且該原始文件有一個或幾個硬鏈接。原始文件存儲在HFS +私有數(shù)據(jù)中，并且具有類似iNode1234567的名稱。例如，我們有文件“?file1.txt?”，并為此文件創(chuàng)建一個硬鏈接“?file2.txt?”。現(xiàn)在，我們在HFS +私有數(shù)據(jù)目錄中有一個原始文件，并且有兩個硬鏈接（file1.txt?‘和’?file2.txt）。
For HFS+ file system, there are one original file, and one or several hard links for this original file. Original files are stored in?HFS+ Private Data?and have names like?iNode1234567. For example, we have file ‘file1.txt‘ and create a hard link ‘file2.txt‘ for this file. Now we have one original file in the HFS+ Private Data catalog and two hard links (file1.txt‘ and ‘file2.txt).

目錄的硬鏈接原件存儲在..HFS+ Private Directory Data_文件夾中
Hard link originals for catalogs are stored in?.HFS+ Private Directory Data_?folder.

HFS +文件系統(tǒng)中Time Machine的數(shù)據(jù)結構?The data structure of the Time Machine in the HFS+ file system

詳細信息取決于最終用戶的設置，但通常，Time Machine將數(shù)據(jù)保存在Backups.backupdb文件夾或該文件夾中的名稱包含單詞“ Time Machine”的HFS +分區(qū)上。此文件夾或具有用戶名的文件夾都具有一組目錄，這些目錄的格式類似YYYY-MM-DD-hhmmss（年，月，日，時，分，秒）
Details depend on the end-user settings, but in general, Time Machine saves data on HFS+ partition in?Backups.backupdb?folder or the folder, which name contains words “Time Machine”. Either this folder or a folder with username has a set of catalogs with masl likeYYYY-MM-DD-hhmmss (year, month, day, hour, minute, second).

如果打開其中一個目錄，則可以看到目錄名稱中提到的確切日期和時間的文件系統(tǒng)快照。顯然，大多數(shù)文件更改的頻率低于創(chuàng)建副本的頻率，因此Time Machine不會復制未更改的文件，而是為這些文件創(chuàng)建硬鏈接。它充分減少了快照創(chuàng)建時間和已用空間。但是，此結構使Time Machine的數(shù)據(jù)恢復過程復雜化。
If we open one of these catalogs we can see a snapshot of the file system at exact date and time mentioned in catalog name. Obviously the most of the files are changed less commonly than the copies are created, so?Time Machine doesn’t copy unchanged files, it creates hard links for these files. It sufficiently decreases snapshot creation time and used space. However, this structure complicates the data recovery process from Time Machine.

此外，Time Machine不是唯一使用硬鏈接的地方，而是這些硬鏈接最常使用的地方
Besides, the Time Machine is not the only place where the hard links are used, but that’s where these links are most frequently used.

數(shù)據(jù)提取器中具有硬鏈接的操作方法?Modus operandi?with hard links in Data Extractor

在Data Extractor中使用硬鏈接的主要功能是過渡到原始文件：
The main feature with hard link working in Data Extractor?is the transitioning to the original file:

• 如果我們嘗試為硬鏈接構建映射，則會構建原始文件的映射。
  if we try to build a map for a hard link, a map of the original file is built;
• 如果我們保存硬鏈接，則原始文件的數(shù)據(jù)將以硬鏈接的名稱保存。
  if we save the hard link, the data of the original file is saved under the name of the hard link.

這對于從存在物理問題的磁盤中恢復數(shù)據(jù)非常有用。我們構建所需數(shù)據(jù)的地圖，讀取此地圖，然后保存數(shù)據(jù)
This is very useful for recovering data from disks with physical issues. We build a map of needed data, we read this map, we save the data.

但是，保存數(shù)據(jù)的大小存在問題。由于硬鏈接，它大大增加了。
However, there is a problem with the size of the saved data. It increases?enormously?due to hard links.

• 每個原始文件可以具有數(shù)十個硬鏈接。對于每個硬鏈接，都會構建原始文件的地圖并將其添加到總地圖中。因此，總圖的大小可能比整個驅動器的大小大。
  each original file can have a few tens of hard links. For each hard link, the map of the original file is built and added to the total map. So the size of the total map can be way more than the size of the whole drive.
• 每個硬鏈接都保存為單獨的文件。因此，已保存文件的大小可能大大超過整個驅動器的大小。
  each hard link is saved as a separate file. So the size of saved files can be massively more than the size of the whole drive.

具有硬鏈接的數(shù)據(jù)恢復過程的解決方案?The solution for the data recovery process with hard links

• 如果您的客戶端不需要所有Time Machine數(shù)據(jù)，則不要構建也不保存Time Machine（\ Backups.backupdb）目錄的映射。另外，您可以跳過文件夾?HFS+ Private Data?and .HFS+ Private Directory Data_
  Do not build and do not save the map of Time Machine (\Backups.backupdb) catalog if your client doesn’t need ALL Time Machine data. Also, you can skip folders?HFS+ Private Data?and .HFS+ Private Directory Data_
• 在Time Machine中建立并創(chuàng)建最后一個快照的映射（如果最后一個快照沒有任何有效數(shù)據(jù)，則可能是先前快照的映射
  Build and create a map of the last snapshot in Time Machine (maybe a map of previous snapshots if the last one doesn’t have any valid data
• 使用地圖壓縮來估計已保存數(shù)據(jù)的實際大小(參考:使用PC-3000 Data Extractor怎么恢復$MFT位圖上有壞扇區(qū)的數(shù)據(jù)？一文）
  Use?map compressing?to estimate the real size of saved data
  

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