<p class="shortdesc"></p> <section class="section" id="eliability__section_blc_krc_rlb"><h2 class="doc-tairway">Overview</h2> <p class="p">EBS ensures high reliability of data via the three-copies of data technology, EBS disk snapshot, and EBS disk backup. </p> <ul class="ul" id="eliability__ul_kkk_krc_rlb"> <li class="li">Three-copies of data mechanism is a technology provided by EBS storage system to ensure high reliability of data. This technology is mainly used to deal with data loss or data inconsistency caused by hardware device failure. </li> <li class="li">EBS disk snapshot and EBS disk backup are mainly used to back up and restore data in the case of data loss or data inconsistency caused by misoperations, hacker attacks, or virus intrusions.</li> </ul> </section> <section class="section" id="eliability__section_c1p_krc_rlb"><h2 class="doc-tairway">Three-copies of Data Technology</h2> <p class="p">EBS adopts the three-copies of data mechanism to back up data on different physical servers. In this way, it effectively avoids the data loss caused by a single node failure and improves the reliability of stored data. </p> <p class="p">In this mechanism, one piece of data is by default divided into multiple 4 MB data blocks. Each data block is saved in three copies, and these copies are stored on different nodes in the system according to the distributed algorithms. As shown below, the storage system will back up data block P1 on storage node A to P1’ on storage node B and to P1'' on storage node C at the same time. Data blocks P1, P1', and P1'' are the three copies of the same data block.</p> <img class="image" id="eliability__image_et2_bsc_rlb" src="https://obs-cn-shanghai.yun.pingan.com/pcp-portal/20200707171849-18caebd99bba.png" width="800"> <p class="p">Any changes (addition, modification, or deletion) to the stored data will be executed simultaneously on three copies. The system returns success response only after operations on the three copies are all finished. In this way, tight consistency of data among the three copies can be effectively ensured. </p> <p class="p">If a storage node fails or a disk of the storage node fails, the system will start automatic restoration mechanism to rebuild and restore data on other storage nodes simultaneously without affecting the normal operation of business. </p> </section> <section class="section" id="eliability__section_c54_lrc_rlb"><h2 class="doc-tairway">EBS Disk Snapshot</h2> <p class="p">An EBS disk snapshot is a complete copy or image of the disk data at a specific time point. As a major disaster recovery approach, you can use a snapshot to completely restore the data to the time point when the snapshot was created.</p> <p class="p">You can create snapshots manually to rapidly save the disk data at a designated time point. In addition, you can use snapshots to create new EBS disks so that the disks will contain the snapshot data in the beginning.</p> <p class="p">Automatic creation of snapshots can be realized by configuring snapshot policies. According to the snapshot policies configured, the system will periodically (such as daily, weekly, or monthly) create snapshots for associated EBS disks. You can also designate the time point of the snapshots and set the number of snapshots to be stored so as to facilitate the recovery operation in case of data loss.</p> <p class="p">In the case of data loss, you can restore data by rolling back the disk. However, snapshot data can be rolled back only to its source EBS disk. A rollback to other EBS disks is not supported.</p> <p class="p">Currently, snapshots provide full backup, and incremental backup can be realized in the future. That means only data on the device that has been modified after the latest snapshots are created will be saved. This will shorten as much as possible the time required to create snapshots and save storage costs.</p> <div class="note note note_note"><span class="note__title">Note:</span> The snapshot function is now for free. </div> <p class="p">The snapshot function is mainly applied to the following scenarios: </p> <ul class="ul" id="eliability__ul_abc_4rc_rlb"> <li class="li"><strong class="ph b">Routine data backup</strong><p class="p">You can create snapshots for EBS disks on a regular basis and use snapshots to back up your data in case that data loss or data inconsistency occurs due to misoperations, viruses, or hacker attacks.</p></li> <li class="li"><strong class="ph b">Rapid data restoration</strong><p class="p">You can create a snapshot or multiple snapshots before you change an operating system, upgrade an application software, or migrate service data. If an exception occurs during the upgrade or migration, service data can be rapidly restored to the time point when the snapshot was created. For example, a fault occurs on system disk A of server A, and therefore server A cannot be started. Because system disk A has already failed, the data on system disk A cannot be restored by rolling back snapshots. However, you can create disk B using an existing snapshot of system disk A and mount disk B to a properly running server, such as server B. In this case, server B can read the data of system disk A from disk B.</p></li> <li class="li"><strong class="ph b">Multi-service quick deployment</strong><p class="p">You can use a snapshot to create multiple disks containing the same data, and these disks can be used as data resources for various services, such as data mining, report query, and development and testing. This method protects the initial data and deploys other services rapidly through the disks created from snapshots, meeting the diversified requirements of enterprises for service data.</p></li> </ul> </section> <section class="section" id="eliability__section_c5m_qrc_rlb"><h2 class="doc-tairway">EBS Disk Backup </h2> <p class="p">Ping An Cloud provides users with CBS (Cloud Backup Service), which can back up data files on designated servers according to customized backup policies. </p> <p class="p">You can create a backup policy or multiple backup policies, and each policy will back up a directory or file on a regular basis. In the case of data loss, you can restore the backup data to the designated server. You can also modify, delete, or disable the backup policies as required. </p> <p class="p">CBS is commonly applied to the following scenarios: </p> <ul class="ul" id="eliability__ul_nqb_rrc_rlb"> <li class="li"><strong class="ph b">Accidental deletion or overwriting of initial data </strong><p class="p">CBS can instantly restore data to the backup point prior to the accidental deletion. Thus, it can effectively prevents inadvertent loss of important data. </p></li> <li class="li"><strong class="ph b">Application update errors</strong><p class="p">CBS can instantly restore a server or disk to the backup point prior to the application update. </p></li> <li class="li"><strong class="ph b">System breakdown</strong><p class="p">CBS can instantly restore a server to the backup point prior to the system breakdown.</p></li> <li class="li"><strong class="ph b">Remote data replication </strong><p class="p">CBS can restore backup data to multiple designated servers. </p><p class="p">For more information about the detailed description of and guidance on EBS disk backup, see <a class="xref" href="https://pinganyun.com/ssr/help/storage/cbs/index.overview" target="_blank">CBS</a>. </p></li> </ul> </section> <section class="section" id="eliability__section_d23_trc_rlb"><h2 class="doc-tairway">Differences Between EBS Disk Snapshot and EBS Disk Backup </h2> <table class="table" id="eliability__table_umw_trc_rlb"><caption></caption><colgroup><col><col><col></colgroup><thead class="thead"> <tr class="row"> <th class="entry" id="eliability__table_umw_trc_rlb__entry__1">Comparison Item</th> <th class="entry" id="eliability__table_umw_trc_rlb__entry__2">EBS Disk Snapshot</th> <th class="entry" id="eliability__table_umw_trc_rlb__entry__3">EBS Disk Backup</th> </tr> </thead><tbody class="tbody"> <tr class="row"> <td class="entry" headers="eliability__table_umw_trc_rlb__entry__1 "> <p class="p">Data Storage</p> </td> <td class="entry" headers="eliability__table_umw_trc_rlb__entry__2 "> <p class="p">EBS disk snapshot is stored in OBS. </p> </td> <td class="entry" headers="eliability__table_umw_trc_rlb__entry__3 "> <p class="p">EBS disk backup data is stored in OBS.</p> </td> </tr> <tr class="row"> <td class="entry" headers="eliability__table_umw_trc_rlb__entry__1 "> <p class="p">Backup Method </p> </td> <td class="entry" headers="eliability__table_umw_trc_rlb__entry__2 "> <p class="p">By creating manual snapshots or snapshot policies, you can save data on the disk at a designated time. </p> </td> <td class="entry" headers="eliability__table_umw_trc_rlb__entry__3 "> <p class="p">By creating backup policies, you can back up data periodically. </p> </td> </tr> <tr class="row"> <td class="entry" headers="eliability__table_umw_trc_rlb__entry__1 "> <p class="p">Backup Range </p> </td> <td class="entry" headers="eliability__table_umw_trc_rlb__entry__2 "> <p class="p">All data on the disk can be backed up. You cannot select a directory to save data. </p> </td> <td class="entry" headers="eliability__table_umw_trc_rlb__entry__3 "> <p class="p">Select a directory to save data. Selecting the root directory is not supported. </p> </td> </tr> <tr class="row"> <td class="entry" headers="eliability__table_umw_trc_rlb__entry__1 "> <p class="p">Backup Region</p> </td> <td class="entry" headers="eliability__table_umw_trc_rlb__entry__2 "> <p class="p">Same availability zone</p> </td> <td class="entry" headers="eliability__table_umw_trc_rlb__entry__3 "> <p class="p">Same region</p> </td> </tr> <tr class="row"> <td class="entry" headers="eliability__table_umw_trc_rlb__entry__1 "> <p class="p">Service Recovery </p> </td> <td class="entry" headers="eliability__table_umw_trc_rlb__entry__2 "> <p class="p">You can restore the data saved by rolling back snapshots or creating EBS disks from snapshots. </p> </td> <td class="entry" headers="eliability__table_umw_trc_rlb__entry__3 "> <p class="p">You can restore the backup data via the operation recovery function.</p> </td> </tr> </tbody></table> </section>