Replication

The DXi provides data replication capabilities that you can use as an integral part of a disaster recovery plan. Replication allows you to configure the DXi to create a copy of your data on any other DXi system on a compatible software version.

Note: Quantum strongly advises creating a dedicated share for each backup application. Not only is this easiest for storage management, but some backup applications do not release files immediately so there is a potential for conflicts, particularly with replicated shares.

In the event of a disaster or ransomware attack, you can quickly recover the replicated data on the remote system, allowing your business to resume normal operations. Once the original system is available again, you can restore all data back to its original location.

Note: If you have more than one IP address configured on your DXi’s network page, it is highly recommended to implement static routes to the replication partner (both from source to target and from target to source). See Understanding Interface Routing for more information.

Additional Information

During data replication, data is sent from one system (the source) to another system, usually in another location (the target). For example, you might replicate data from a branch office to a central office.

Replication works only with deduplicated data, and data is compressed before it is replicated. Because of this, the amount of data transmitted between systems during replication is greatly reduced compared to the original amount of data stored. In addition, a data block is transmitted only if the target does not already have a copy of the block. Finally, data can optionally be encrypted before it is transmitted.

DXi supports two types of replication:

Namespace replication works by constantly sending deduplicated data to the target system, and then either by schedule or manually, creating a snapshot on the target system. this gives you a point-in-time snapshot of the stored data that remains until the snapshot is deleted. The number of snapshots that are maintained is controlled by the receiving system.

If the sending DXi is lost or data is corrupted, a "restore" operation can be run from the receiving DXi to re-create the data exactly as it was at the time the snapshot was sent.

After you recover a share, it is re-created on the target system and is available for use. After the source system becomes available again, you can perform a failback operation to restore the share to its original location.

Caution: A saved snapshot is necessary to recover your data at a later time. For this reason, it is not enough to simply enable replication for a share. You must also configure a replication schedule (recommended) or perform manual replication on a regular basis to send snapshots of the share to the target system.

Like Namespace replication, Directory/File-based replication constantly sends data from a share on the source to a share on another DXi. But it is different in a number of ways:

  • Data is mirrored between the source and target systems and both have all the same files available at the same time (no snapshots for a point in time).

  • A unique Sync ID is used to associate the replicated share on the source system with the share that will receive the replicated data on the target system.

  • You do not need to schedule or manually perform share through the remote management console. Instead, replication is triggered when a file is closed or a period of time after it is modified (NAS shares).

  • After directories/files are replicated using Directory/File-based Replication, they are automatically recovered on the target system and are immediately available for use. There is no need to first recover the share to access its data.
  • Deletions are automatically propagated from the source system to the target system in order to free up space on the target. In addition, you can manually initiate a synchronization from the source system at any time. Synchronizing ensures that the contents of the source share are exactly the same as the target share.

Additional Information

  • For CIFS/SMB shares, a file is replicated immediately after it is closed. For NFS shares, a file is replicated after it has been idle (not accessed) for several minutes.

  • To optimize the replication process, deduplicated data is continuously sent in the background from the source system to the target system. Any remaining data is sent (along with metadata) at the time a file is closed.

  • If you delete a share configured for Directory/File Based Replication on the source DXi, the share is not automatically deleted on the target. If you do not want to retain the share on the target DXi, you can manually delete it.

  • Snapshots for a point in time can be created and protected on the target replication system using Secure Snapshots. But deleting these snapshots is not allowed and they must expire based on retention days.

The DXi can duplicate the data on an LSU (logical storage unit) to another location using the OST optimized duplication (OST replication) feature supported by Veritas NetBackup and Backup Exec. If you are using Veritas NetBackup 7.1 or higher, you can configure an LSU for Automatic Image Replication.

For information about configuring and using OST optimized duplication and Automatic Image Replication, see Replicating OST Data.

The DXi can send replicated data to multiple target systems. First, configure up to two replication targets. Then for each share, select which targets where you will replicate data, to one, both, or neither. See Adding a Replication Target and Enabling Share Replication .

Below are three possible scenarios in which multiple replication targets are configured.

All Shares Replicate to Multiple Targets

For enhanced disaster recovery, all shares on the DXi are configured to replicate to multiple targets. In this scenario, even if one target system is lost, the other target system still retains a full copy of all data on the source DXi.

Some Shares Replicate to Multiple Targets

For increased flexibility, each share on the DXi is configured to replicate only to the targets where needed. In this scenario, share fall into three categories:

  • Some shares replicate to Target 1. (They may also replicate to Target 2.)
  • Some shares replicate to Target 2. (They may also replicate to Target 1.)
  • Some shares are not replicated.

The Replication page allows you to set up replication for NAS or Application Specific shares, and to replicate and recover data.

To access the Replication page, click the Replication menu.

The Replication page contains the following tabs:

Task Overview

Use the DXi data replication features to perform the following tasks:

To replicate all data on a NAS share from a source system to a target system:

  1. On the target system, add the source system to the list of allowed replication sources. See Adding a Replication Source.
  2. On the source system, specify the target system that will receive replicated data. See Adding a Replication Target.
  3. On the source system, create a new share with deduplication enabled. See Adding a NAS Share.
  4. Enable replication for the new share. See Enabling Share Replication.

  5. Before writing any data to the new share, replicate the new share. See Replicating a Share.

    Quantum recommends that you always replicate a new share immediately after creating it. This establishes the initial data structure on the target system and greatly increases the speed of the first replication.

  6. Choose one of the following methods to regularly replicate the new share:

After replication, a snapshot is sent to the target system. You can use the snapshot to recover the replicated share on the target system or restore the share to its original location on the source system. See Task Overview: Recovering a Namespace Replicated Share and Task Overview: Performing a Share Failback.

Important Information: Setting up and Performing Replication

  • If you are setting up "namespace" type replication and do not configure a replication schedule or manually replicate the share on a regular basis, your data is not protected. While the DXi continually sends data to the target system in the background to optimize the replication process, a snapshot that preserves the complete structure of your data is sent to the target system only when a scheduled or manual replication job occurs. If you do not regularly and frequently replicate your data as described in Step 6 above, it cannot be restored at a later time.
  • If a replication is not scheduled or run manually for namespace-type replication, data is still continuously sent to the target once replication is configured on the source DXi. This can potentially fill up the target DXi.

Note: Directory/File-based replication normally mirrors the source share to the target share. Point-in-time snapshots of the data can be created on the source or target, however, with DXi Secure Snapshots.

To automatically replicate directories/files from a source system and immediately recover them for use on a target system:

  1. Perform the following steps on the target system:

    1. Add the source system to the list of allowed replication sources. See Adding a Replication Source.
    2. Create a new share with deduplication enabled. See Adding a NAS Share.
    3. Enable Directory/File-based Replication for the new share and specify the Sync ID. See Replication Configuration.

  2. Perform the following steps on the source system:

    1. Specify the target system that will receive replicated data. See Adding a Replication Target.
    2. Create a new share with deduplication enabled. See Adding a NAS Share.
    3. Enable Directory/File-based Replication for the new share and specify the Sync ID. See Replication Configuration.

A file is automatically replicated when it is closed or a period of time after it is modified. After replication, the replicated directories/files are immediately available on the target system. There is no need to recover the share to make the directories/files available.

If a NAS share is lost or damaged on the source system, you can recover it on the target system using a received snapshot. When you recover a share, it is recreated on the target system just as it was at the point in time when the snapshot was saved.

To recover a replicated share:

  1. On the target system, select a received snapshot and perform a recover operation. See Recovering a Share.

    The share is now available on the target system.

  2. (Optional) Map your backup application to the recovered share on the target system to continue making backups.

  3. When the source system is operating correctly again, choose one of the following actions:

    • Failback the share to restore it on the original source system. Then, if necessary, map your backup application to the restored share on the original source system. See Task Overview: Performing a Share Failback.
    • Continue to make backups to the recovered share on the original target system. In addition, set up replication to replicate the share back to the original source system. In this scenario, the original source system is now the target, and the original target system is now the source. See Task Overview: Setting Up and Performing Namespace Replication.

Note: When you failback a share, the snapshot from the point in time of the original replication is replicated back to the original replication source. This snapshot then needs to be recovered. See Recovering a Share.

If a NAS share is lost or damaged on the source system, you can failback the share to the source system using a received snapshot on the target system. When you failback a share, it is restored on the source system just as it was at the point in time when the snapshot was saved.

To perform a share failback:

  1. On the original source system, add the original target system to the list of allowed replication sources See Adding a Replication Source.

    Note: For the purposes of failback, the original source system is now acting as a target because it will receive the snapshot from the original target system.

  2. On the original target system, select a received snapshot and perform a failback operation pointing to the original source system, and then recover the share on the original source system. See Performing a Failback For a Share.

    The share is now available on the original source system.

  3. (Optional) If necessary, map your backup application to the restored share on the original source system.