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OceanStor 9000 V300R006C00 File System Feature Guide 12

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Huawei uses machine translation combined with human proofreading to translate this document to different languages in order to help you better understand the content of this document. Note: Even the most advanced machine translation cannot match the quality of professional translators. Huawei shall not bear any responsibility for translation accuracy and it is recommended that you refer to the English document (a link for which has been provided).
Working Principles

Working Principles

This section describes the related concepts and working principles of the Network Data Management Protocol (NDMP) backup feature.

Related Concepts

This section describes the concepts related to the Network Data Management Protocol (NDMP) backup feature, helping users understand the working principles of the NDMP backup feature.

The NDMP backup feature of the OceanStor 9000 adopts the 3-way networking mode, as shown in Figure 13-1. This networking mode allows multiple clusters to share backup media and overcomes the distance limitation between the primary and secondary storage.

Figure 13-1  NDMP backup networking diagram
In the OceanStor 9000, the backup server uses a fixed IP address. Data transfer over the network supported by NDMP backup has security risks because data is not encrypted during transfer. It is recommended that you use physical isolation or end-to-end encryption to ensure data transfer security.

The storage layer consists of the primary storage, secondary storage, and backup server, as shown in Figure 13-1.

  • As the primary storage or backup storage source, the OceanStor 9000 stores daily service data.
  • The secondary storage is known as backup media and is used to store backup data. In this document, tape libraries are backup media.
  • A backup server is a server where backup software is deployed and is responsible for processing all backup operations. In this document, the backup software takes NetBackup as an example.

    A backup server can serve as a primary server or a media server based on its functionality.

    • Primary server: Processes and manages backup and recovery services.
    • Media server: Controls backup media.

The NDMP service layer consists of an NDMP server and an NDMP client.

  • As an NDMP server, the OceanStor 9000 is the host for running the NDMP service, is responsible for receiving backup or recovery control commands from the NDMP client, and completes data backup and recovery.
  • As an NDMP client, the backup server is responsible for enabling and controlling NDMP backup and recovery services, creating and controlling NDMP sessions, and accessing, storing, and managing all session states.

Backup and Recovery Modes

This section describes backup and recovery modes of the Network Data Management Protocol (NDMP) feature, including snapshot-based, source directory-based, full backup, incremental backup, full recovery, DAR, and non-DAR recovery modes.

Backup Modes

Table 13-3 describes backup modes of the NDMP backup feature in terms of backup data source.

Table 13-3  Backup modes of the NDMP backup feature in terms of the backup data source

Backup Mode

Description

Snapshot-based backup

The OceanStor 9000 backs up snapshot data created at a specific point in time to ensure data consistency.

Source directory-based backup

The OceanStor 9000 captures data from the file system and backs up the data. If there are write operations during the backup, data consistency cannot be ensured.

By default, the OceanStor 9000 backs up data in snapshot-based mode. You can set other backup modes on the command-line interface (CLI). When snapshot-based backup is enabled, the system creates snapshots for the directories to be backed up and then accesses snapshot data for backup. When data backup is completed, the system deletes snapshots.

Table 13-4 describes backup modes of the NDMP backup feature in terms of backup contents.

Table 13-4  Backup modes of the NDMP backup feature in terms of the backup content

Backup Mode

Description

Full Backup

All data is backed up to the tape libraries.

Differential Incremental Backup

Only the files changed since last backup are backed up.

Cumulative Incremental Backup

Only the files changed since last full backup are backed up.

NOTE:
The definition of incremental backup may vary depending on different backup software. In this document, the definition of incremental backup is given based on NetBackup.

The NDMP backup feature records each backup point in time. When performing incremental backup, the NDMP backup feature refers to the last backup point in time and then accesses file ctime (content, permission, owner, owning group, link count, and last state change time of the file) and mtime (last content change time of the file). If ctime or mtime is later than the last backup point in time, the file is considered to be changed since last backup and needs to perform incremental backup. You can ignore the ctime property by setting so on the CLI. Then you can only compare mtime with last backup point in time. For details, see Managing NDMP Backup on the CLI.

After a hard link is created for a file, mtime of the source file is not changed and is the same as that of the hard link, but ctime of the source file and hard link are changed to the point in time when the hard link is created. In this case,

When snapshot-based backup is disabled, and you perform incremental backup on the file for which you create a hard link after the last backup, two conditions may occur:
  • If ctime is ignored, neither the hard link nor the source file is backed up.
  • If ctime is not ignored, both the hard link and the source file are backed up.

When snapshot-based backup is enabled, the hard link is not backed up because hard link is not under the protection of snapshot.

NOTE:
A hard link is a physical index of a file in a file system. A hard link can be executed, edited, or accessed like a common file. A change made to a hard link is a change made to the source file.
Recovery Modes

Table 13-5 descries the recover modes of the NDMP backup feature.

Table 13-5  NDMP backup modes

Recovery Mode

Description

Full Recovery

All data is recovered.

Direct Access Recovery (DAR)

Backup software locates and accesses specific data based on user requirements and then recovers it.

Non-DAR

Backup software finds data to be recovered in tape libraries and then recovers it.

Data Backup Process

This section describes the data backup process of Network Data Management Protocol (NDMP) backup.

Introduction to the Backup Process

The main function of the NDMP backup feature is backup. Backup is a process of replicating data from the OceanStor 9000 primary storage to the secondary storage. The replicated data serves as the copy of the original data and is used to recover data due to a system crash or misoperation.

Figure 13-2 shows the backup flowchart of NDMP backup in OceanStor 9000.

Figure 13-2  NDMP backup flowchart
Establishing Backup Control Connections

Figure 13-3 shows how to establish backup control connections.

Figure 13-3  Establishing backup control connections
  1. Establish a control connection between an NDMP client (backup server) and a tape library.
    1. The primary server sends a control connection request to the media server.
    2. The media server establishes a control connection with the tape library.
    3. The media server sends a message to the primary server, stating that the connection is successfully established.
  2. Establish a control connection between an NDMP client (backup server) and an NDMP server (OceanStor 9000).
    1. The primary server sends a control connection request to the NDMP server (OceanStor 9000).
    2. The NDMP server (OceanStor 9000) authenticates the NDMP client (backup server) and sends a message to the primary server, stating that the connection is successfully established.
      NDMP backup supports only the MD5-challenge-Auth authentication. To meet compatibility requirements (posed by NDMP), NDMP that is usually used on the local area network (LAN) adopts MD5 although the MD5 algorithm is not secure. If NDMP is used on a non-LAN, MD5 poses security risks.
Backing Up Data

Figure 13-4 shows how to back up data.

Figure 13-4  NDMP data backup
  1. Establish a data connection between the OceanStor 9000 and a tape library.
    1. The primary server sends a data connection request to the OceanStor 9000.
    2. The primary server sends a data connection request to the media server.
    3. The media server establishes a data connection with the tape library.
  2. Start backing up data.
Breaking Backup Control Connections

Figure 13-5 shows how to break backup control connections.

Figure 13-5  Breaking backup control connections
  1. The NDMP server (OceanStor 9000) sends a message to the NDMP client (backup server), stating that backup is completed.
  2. The NDMP client (backup server) breaks control connections.
    1. The primary server breaks the control connection with the NDMP server (OceanStor 9000).
    2. The primary server breaks the control connection with the media server.
    3. The media server breaks the control connection with the tape library.

Data Recovery Process

This section describes the data recovery process.

Introduction to the Recovery Process

When data is lost due to a system crash or misoperation, Network Backup Management Protocol (NDMP) can be used to recover the backup data. Backup data becomes meaningless if it cannot be recovered. Recovering data is the main purpose of NDMP backup.

Figure 13-6 shows the backup flowchart of NDMP recovery in OceanStor 9000.

Figure 13-6  NDMP recovery flowchart
Establishing Recovery Control Connections

Figure 13-7 shows how to establish recovery control connections.

Figure 13-7  Establishing recovery control connections
  1. Establish a control connection between an NDMP client (backup server) and a tape library.
    1. The primary server sends a control connection request to the media server.
    2. The media server establishes a control connection with the tape library.
    3. The media server sends a message to the primary server, stating that the connection is successfully established.
  2. Establish a control connection between an NDMP client (backup server) and an NDMP server (OceanStor 9000).
    1. The primary server sends a control connection request to the NDMP server (OceanStor 9000).
    2. The NDMP server (OceanStor 9000) authenticates the NDMP client (backup server) and sends a message to the primary server, stating that the connection is successfully established.
      NDMP backup supports only the MD5-challenge-Auth authentication. To meet compatibility requirements (posed by NDMP), NDMP that is usually used on the local area network (LAN) backup adopts MD5 although the MD5 algorithm is not secure. If NDMP is used on a non-LAN, MD5 poses security risks.
Recovering Data

Figure 13-8 shows how to recover data.

Figure 13-8  NDMP data recovery
  1. Establish a data connection between the OceanStor 9000 and a tape library.
    1. The primary server sends a data connection request to the OceanStor 9000.
    2. The primary server sends a data connection request to the media server.
    3. The media server establishes a data connection with the tape library.
  2. Start recovering data.
Breaking Recovery Control Connections

Figure 13-9 shows how to break recovery control connections.

Figure 13-9  Breaking recovery control connections
  1. The NDMP server (OceanStor 9000) sends a message to the NDMP client (backup server), stating that recovery is completed.
  2. The NDMP client (backup server) breaks control connections.
    1. The primary server breaks the control connection with the NDMP server (OceanStor 9000).
    2. The primary server breaks the control connection with the media server.
    3. The media server breaks the control connection with the tape library.
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Updated: 2019-06-27

Document ID: EDOC1000122519

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