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Backup Preparations

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Before backing up your cluster or replica set, decide how to back up the data and what data to back up. This page describes items you must consider before starting a backup.

See also

To learn how Backup works, see Backup.

Warning

Ops Manager no longer supports the creation of cluster snapshots from database deployments that use local key encryption. If you encrypt a database deployment with local key encryption, the snapshot fails. To encrypt snapshots, use KMIP-based encryption with your database deployments.

Backup Configuration Options

The backup and recovery requirements of a given system vary to meet the cost, performance and data protection standards the system’s owner sets.

Ops Manager Enterprise Backup and Recovery supports five backup architectures, each with its own strengths and trade-offs. Consider the architecture that meets the data protection requirements for your deployment before configuring and deploying your backup architecture.

Example

Consider a system whose requirements include low operational costs. The system’s owners may have strict limits on what they can spend on storage for their backup and recovery configuration. They may accept a longer recovery time as a result.

Conversely, consider a system whose requirements include a low Recovery Time Objective. The system’s owners tolerate greater storage costs if it results in a backup and recovery configuration that fulfills the recovery requirements.

Ops Manager Enterprise Backup and recovery supports the following backup architectures:

  • A file system on a SAN with advanced features for filesystem backups, such as high availability, compression, or deduplication
  • A file system on one or more NAS devices
  • An AWS S3 blockstore
  • MongoDB blockstore in a highly available configuration
  • MongoDB blockstore in a standalone configuration

Important

We provide the backup architecture recommendations as guidance for developing your own data protection approaches. Our recommendations don’t cover or represent each scenario or deployment.

Backup Method Features

Backup System Feature File System on SAN File System on NAS AWS S3 Blockstore MongoDB HA Blockstore MongoDB Blockstore
Snapshot Types Complete [1] Complete [1] Many partial Many partial Many partial
Backup Data Deduplication If SAN supports No Yes Yes Yes
Backup Data Compression Yes Depends [2] Yes Yes Yes
Backup Data Replication If SAN supports No No Yes No
Backup Storage Cost Higher Medium Lower Higher Lower
Staff Time to Manage Backups Medium Medium Lower Higher Medium
Backup RTO Lower Medium Lower Lower Medium
[1](1, 2) To perform an incremental backup to a File System Store, the MongoDB Agent slices each storage engine file in the path specified for backup into block(s) of data and transfers only changed block(s) to Ops Manager. Ops Manager creates a new snapshot from received block(s) and copies the remaining unchanged block(s) from the previous full backup snapshot. Each incremental backup snapshot stored to a file system saves network I/O. Each such backup snapshot contains a full copy of all required files from a backed up MongoDB deployment and does not de-duplicate records.
[2]Ops Manager 4.4.5 and later ignores GZIP compression for File System Store. Trying to create snapshots to File System Stores using GZIP compression fails in previous Ops Manager versions.

Note

When Do You Use a Particular Backup Method?

  • To run backups frequently on large amounts of data and restore from backups, consider backing up to a file system on a SAN, an AWS S3 snapshot store, or a MongoDB blockstore configured as a replica set or a sharded cluster.

  • To restore data without relying on MongoDB database, consider backing up to an AWS S3 snapshot store, one or more NAS devices, or a file system on a SAN with advanced features for file system backups, such as high availability, compression, or deduplication.

  • To minimize internal storage and maintenance costs, consider backing up to an AWS S3 snapshot store or a MongoDB standalone blockstore.

    A MongoDB standalone blockstore offers limited resilience. If the disk fills, this blockstore may go offline. You can recover backup snapshots only after adding additional storage.

Backup Sizing Recommendation

When sizing the backup of your data, keep the replica set size to 2 TB or less of uncompressed data. If your database increases beyond 2 TB of uncompressed data:

  • Shard the database
  • Keep each shard to 2 TB or less of uncompressed data

These size recommendations are a best practice. They are not a limitation of the MongoDB database or Ops Manager.

Backup and restore can use large amounts of CPU, memory, storage, and network bandwidth.

Example

Your stated network throughput, such as 10 Gbps or 100 Gbps, is a theoretical maximum. That value doesn’t account for sharing or throttling of network traffic.

Consider the following scenario:

  • You want to back up a 2 TB database.
  • Your hosts support a 10 Gbps TCP connection from Ops Manager to its backup storage.
  • The network connection has very low packet loss and a low round trip delay time.

A full backup of your data would take more than 30 hours to complete. [*]

This doesn’t account for disk read and write speeds, which can be, at most, 3 Gbps reads and 1 Gbps writes for a single or mirrored NVMe storage device.

The time required to complete each successive incremental backup depends on write load.

If you shard this database into 4 shards, each shard runs its backup separately. This results in a backup that takes less than 8 hours to complete.

[*]These throughput figures were calculated using the Network Throughput Calculator and assume no additional network compression.

Snapshot Frequency and Retention Policy

By default, Ops Manager takes a base snapshot of your data every 24 hours.

If desired, administrators can change the frequency of base snapshots to 6, 8, 12, or 24 hours. Ops Manager creates snapshots automatically on a schedule; you cannot take snapshots on demand.

Ops Manager retains snapshots for the time periods listed in the following table.

If you terminate a deployment’s backup, Ops Manager immediately deletes the snapshots that are within the dates of the current retention policy.

If you stop a deployment’s backup, Ops Manager stops taking new snapshots but retains existing snapshots until their listed expiration date.

Snapshot Default Retention Policy Maximum Retention Policy
Base snapshot 2 days 5 days (30 days if frequency is 24 hours)
Daily snapshot 0 days 1 year
Weekly snapshot 2 weeks 1 year
Monthly snapshot 1 month 7 years

You can change a backed-up deployment’s schedule through its Edit Snapshot Schedule menu option, available through the Backup page. Administrators can change snapshot frequency and retention through the snapshotSchedule resource in the API.

Changing the reference time changes the time of the next scheduled snapshot. You can’t make the next scheduled snapshot happen sooner than the current next snapshot time. The current next snapshot time is the current reference time plus the interval between snapshots.

To determine the time of the next snapshot, compare the current next snapshot time to the new reference time:

  • If the new reference time is before the current next snapshot time, the next snapshot still occurs after the current next snapshot time. The snapshot occurs at the new reference time plus the number of intervals needed to surpass the current next snapshot time. If this time has already passed when you make the change, the Ops Manager takes the next snapshot at the next occurrence of the new reference time. See the first two rows of the following table for examples.
  • If the new reference time is after the current next snapshot time, Ops Manager takes the next snapshot at the next occurrence of the new reference time. See the third and fourth row of the following table for examples.
Time of Change Current Reference Time Interval Between Snapshots Current Next Snapshot Time New Reference Time Time of Next Snapshot
08:00 UTC 12:00 UTC 6 hours 12:00 UTC 10:00 UTC 16:00 UTC today
23:00 UTC 12:00 UTC 6 hours 00:00 UTC 10:00 UTC 04:00 UTC tomorrow
08:00 UTC 12:00 UTC 6 hours 12:00 UTC 19:00 UTC 19:00 UTC today
20:00 UTC 12:00 UTC 6 hours 00:00 UTC 19:00 UTC 01:00 UTC tomorrow

If you change the schedule to save fewer snapshots, Ops Manager does not delete existing snapshots to conform to the new schedule. To delete unneeded snapshots, see Delete a Snapshot.

Limits

  • Ops Manager does not backup deployments where the total number of collections on the deployment meets or exceeds 100,000.
  • Ops Manager does not replicate index collection options.

Encryption

Ops Manager can encrypt any backup job stored in a head database running MongoDB Enterprise between FCV 3.4 and 4.0 with the WiredTiger storage engine.

See also

Encrypted Backup Snapshots.

Backup Considerations

Consistency and Snapshots

For clusters running MongoDB version 4.2 or and later:

  • Ops Manager maintains causal consistency when taking snapshots except for size statistics reported by collStats and db.[collection].count(). Size statistics reported by collStats and db.[collection].count() may be inccurate.
  • Ops Manager coordinates the time across all shards for sharded clusters. This ensures that snapshots include all documents written to every shard and node as of the scheduled snapshot time.

For clusters running MongoDB version 4.0 and earlier:

  • Ops Manager maintains crash-consistent snapshots.
  • Ops Manager takes snapshots from each of the shards for sharded clusters and the Config Server Replica Sets at approximately the same time.

Databases Running FCV 4.2 and Later

Backup Features Supported at Present

Feature Databases running FCV 4.2 and later Databases running FCV 4.0 and earlier
Backs up Data using WiredTiger Snapshots check circle icon  
Backs up Data using the Backup Daemon   check circle icon
Backs up Replica Sets check circle icon check circle icon
Backs up Sharded Clusters check circle icon check circle icon
Can Filter using Namespaces   check circle icon
Can Specify Sync Source Database   check circle icon
Can Restore Data to Specific Point in Time [3] check circle icon check circle icon
Can Perform Incremental Backups [4] check circle icon check circle icon
Supports Snapshots that use KMIP Encryption [5] check circle icon check circle icon
Supports Snapshots that use Local Key Encryption [6]   check circle icon
Supports Saving to blockstore snapshot storage check circle icon check circle icon
Supports Saving to S3 Snapshot Storage check circle icon check circle icon
Supports Saving to File System Storage [7] check circle icon check circle icon
Supports Databases running MongoDB Enterprise check circle icon check circle icon
Supports Databases running MongoDB Community   check circle icon
Requires a MongoDB Agent with backup enabled on every mongod cluster node check circle icon  
[3]Performing a PIT restore requires Ops Manager 4.2.13 or later.
[4]

Ops Manager requires a full backup for your first backup, after a snapshot has been deleted, and if the blockstore block size has been changed. Incremental backups reduce network transfer and storage costs.

This feature works with:

  • MongoDB 4.0 and earlier.
  • MongoDB 4.2.6 or later if running FCV 4.2 or later.
[5]Querying an encrypted snapshot requires MongoDB Enterprise 4.2.9 and later or 4.4.0 and later.
[6]FCV 4.2 and later backups don’t support local key encryption.
[7]Backups to a FCV 4.2 or later database to a File System Store ignore File System Store Gzip Compression Level.

Requirements and Limitations

To run backups and restores if you are running MongoDB 4.2 or later with FCV 4.2 or later, you:

  • Must run MongoDB Enterprise.
  • Must account for the change in blockstore block size. If you didn’t set your block size and used the default, that block size changes from 64 KB to 1 MB. This can impact storage usage.
  • Can’t use namespace filter lists to define the namespaces included in a backup. Snapshots using FCV 4.2 or later always include all namespaces.
  • Must ensure the hostnames in your replica set configuration match the hostnames that the MongoDB Agent uses, or that your host mappings contain the correct hostnames. You can use rs.conf() to verify your replica set configuration.
  • Don’t need a sync source database. When taking a Snapshot, Ops Manager selects the replica set member with the least performance impact and greatest storage-level duplication of Snapshot data.
  • Must deploy a MongoDB Agent with every mongod node in the cluster.

Note

If Ops Manager doesn’t manage your cluster:

  • Grant the backup and clusterAdmin roles to the MongoDB user that runs backups.
  • Ensure that the operating system user that runs the MongoDB Agent has read permission for all data files (including journal files) of the deployment.
Shared File System

If you configure Ops Manager to use multiple Ops Manager application servers behind an HTTP or HTTPS load balancer and use file system snapshots, FCV 4.2 or later backup snapshot jobs run in parallel on one or more servers. Ensure that you have a shared file system mounted on each Ops Manager server. The Ops Manager application server might open and write different offsets of the same files. Ensure that the shared file system allows this. Otherwise, you will encounter access errors.

Databases Running FCV 4.0 and Earlier

Important

Only sharded clusters or replica sets can be backed up. To back up a standalone mongod process, you must convert it to a single-member replica set.

The following considerations apply when your databases run any version of MongoDB 4.0 or earlier or when they run MongoDB 4.2 with "featureCompatibilityVersion" : 4.0

Garbage Collection of Expired Snapshots

Ops Manager manages expired snapshots using groom jobs. These groom jobs act differently depending upon which snapshot store contains the snapshots:

Snapshot Store How Groom Jobs Work
MongoDB blockstore Uses additional disk space up to the amount of living blocks for each job.
Filesystem snapshot stores Deletes expired snapshots
S3 snapshot stores

For FCV 4.0 or earlier, may use additional disk space if Ops Manager creates a snapshot while the groom job is running.

For FCV 4.2 or later, Ops Manager can’t create snapshots while a groom job is running.

Namespaces Filter

The namespaces filter lets you specify which databases and collections to back up. You create either a Blacklist of those to exclude or a Whitelist of those to include. You make your selections when starting a backup and can later edit them as needed. If you change the filter in a way that adds data to your backup, a resync is required.

Use the blacklist to prevent backup of collections that contain logging data, caches, or other ephemeral data. Excluding these kinds of databases and collections will allow you to reduce backup time and costs. Using a blacklist is often preferable to using a whitelist as a whitelist requires you to intentionally opt in to every namespace you want backed up.

Note

MongoDB deployments with "featureCompatibilityVersion" : 4.2 do not support namespaces filters.

Storage Engine

To back up MongoDB clusters, use the WiredTiger storage engine storage engine.

If your current backing databases use MMAPv1, upgrade to WiredTiger:

With WiredTiger, Ops Manager limits backups to deployments with fewer than 100,000 files. Files includes collections and indexes.

MongoDB 4.2 removes MMAPv1 storage. To learn more about storage engines, see Storage in the MongoDB manual.

Resyncing Production Deployments

For production deployments, resync all backed up replica sets periodically, such as once a year. When you resync, data is read from a secondary in each replica set. During resync, no new snapshots are generated.

You may also want to resync your backup if you:

Checkpoints

Important

You may use checkpoints for clusters that run MongoDB with Feature Compatibility Version of 4.0 or earlier. Checkpoints were removed from MongoDB instances with FCV of 4.2 or later.

For sharded clusters, checkpoints provide additional restore points between snapshots. With checkpoints enabled, Ops Manager creates restoration points at configurable intervals of every 15, 30 or 60 minutes between snapshots. To enable checkpoints, see enable checkpoints.

To create a checkpoint, Ops Manager stops the balancer and inserts a token into the oplog of each shard and config server in the cluster. These checkpoint tokens are lightweight and don’t affect performance or disk use.

Backup doesn’t require checkpoints, and they are disabled by default.

Restoring from a checkpoint requires Ops Manager to apply the oplog of each shard and config server to the last snapshot captured before the checkpoint. Restoration from a checkpoint takes longer than restoration from a snapshot.

Snapshots when Agent Can’t Stop Balancer

For sharded clusters running with FCV 4.0 or earlier, Ops Manager disables the balancer before taking a cluster snapshot. In certain situations, such as a long migration or no running mongos, Ops Manager tries to disable the balancer but cannot. In such cases, Ops Manager continues to take cluster snapshots but flags the snapshots that may have incomplete or inconsistent data. Cluster snapshots taken during an active balancing operation run the risk of data loss or orphaned data.

Snapshots when Agent Can’t Contact a mongod

For sharded clusters, if the Backup can’t reach a mongod process, whether a shard or config server, then the agent can’t insert a synchronization oplog token. In these cases, Ops Manager doesn’t create the snapshot and displays a warning message.

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