Introduction
Apache Cassandra is a popular NoSQL database that provides high availability and fault tolerance through its distributed architecture. However, many enterprises rely solely on Cassandra’s built-in replication mechanisms and fail to implement an effective backup strategy. While Cassandra’s replication can provide resiliency against node failures, it does not protect against data loss due to accidental deletions, application errors, or other disasters.
In this blog post, we will explore why Apache Cassandra should be backed up and how to create an effective backup strategy.
Why should you backup an Apache Cassandra cluster?
1. Cassandra Data Loss Protection
Despite the high availability and fault tolerance offered by Apache Cassandra, data loss can still occur due to a variety of reasons such as human error, malicious attacks, or natural disasters. Backing up the Cassandra database regularly is essential to prevent any catastrophic data loss. With a proper backup strategy in place, enterprises can quickly recover from data corruption or loss and minimize the impact on business operations.
2. Compliance Requirements
Many industries have strict compliance requirements for data retention and protection. For instance, healthcare organizations are required to maintain patient data for a certain period of time, while financial institutions must retain financial records for several years. In such cases, backing up Apache Cassandra regularly is mandatory to meet regulatory compliance requirements.
3. Disaster Recovery
Enterprises can suffer from a range of disasters such as fires, floods, or cyber-attacks that can result in the loss of data. In such scenarios, having a backup of Apache Cassandra can prove to be a lifesaver. By restoring the data from a backup, enterprises can quickly resume their operations and minimize the impact of the disaster on the business.
4. Granular Recovery
Backing up Apache Cassandra can also enable granular recovery of specific data sets or tables. This is particularly useful in situations where only a subset of the data has been corrupted or lost. With a backup, enterprises can restore only the required data instead of restoring the entire database.
5. Testing and Development
Backing up Apache Cassandra can also facilitate testing and development activities. By restoring a backup, developers can create a copy of the production database in a testing environment, enabling them to test new features or application updates without affecting the live data. This can significantly reduce the risk of errors and downtime caused by faulty updates.
What type of failures can occur with Apache Cassandra?
Physical Failures
Even if you are running your workload in the public cloud, there are real physical systems behind the seemingly infinite and API-driven abstractions that engineers are now used to. These are some of the physical failure domains that you will need to cater for, in order to plan your DR strategy.
Server Failures
Bare metal servers and the servers behind your cloud instances or virtual machines will fail. You may be using the remote storage volumes for your Cassandra instances (generally slow and expensive), or local SSDs (ephemeral storage) with higher chances of data loss. Either way, you still need to implement your enterprise architecture with the assumption that these can disappear at any point due to failures.
Data Center Failures
Even a whole data center can have an outage. Some of the common ones I have seen are aircon failures that cause machines to shut down due to heat building up in the buildings. You may have your workload spread across three availability zones. However, they tend to be relatively near each other.
In 2022 one of the availability zones in London experienced an outage due to the unprecedentedly hot summer, and the air conditioning could not keep up (GCP London). Luckily the other two availability zones survived. However, I would suspect this was a pure stroke of luck since the cooling design would likely have been similar across all three zones and the weather conditions did not vary significantly between them.
Entire AWS / GCP regions are known to experience complete outages. The most recent high profile is the GCP Paris region becoming unavailable for a prolonged period.
Even if a problem is contained within one availability zone, the entire userbase attempt to migrate the workload to other AZs in the same region all at the same time, causing outages to the APIs, provisioning, capacity problems etc.
Of course, you should also consider data centers outages due to fire (OVH), flooding (Hurricane Sandy), and other severe weather events that could take out the data centres where you’re running your workload and storing your critical data.
Cassandra provides multi-DC deployment model out of the box. You can mitigate most physical failures using this amazing feature. However, your keyspaces may be configured to have replicas in specific DCs and not others.
Human Errors and Accidents
As CIOs and CTOs, you may have implemented a strong automation culture already, leveraging DevOps/SRE/Infrastructure-as-Code practices. However, even in the most technologically enabled organizations, I have seen time and time again some gremlins that can cause issues with your production data.
One financial services provider leveraging Apache Cassandra to store large volumes of commodity trading data phoned up for help one day. One of the engineers accidentally executed the test environment database cleanup script against their production servers. This script shut down the Cassandra servers and deleted all the SSTable database files.
Unfortunately, this company did not back up their production Cassandra cluster to recover!
Depending on the human errors and the damage they cause, it is extremely difficult to recover from a script that deletes data files from all Cassandra servers in one hit.
Application Issues
Applications writing to Cassandra may inadvertently delete or overwrite some critical data. You will want to recover data from a specific point in time in the past.
Worried? You Should Be!
As business or technology leaders of enterprises, data is one of the challenges that keep you up at night. Fortunately, implementing a backup strategy with Cassandra is not difficult, and it should be done as part of any enterprise deployment of Cassandra.
How to Backup Your Cassandra Cluster
To backup a Cassandra server, you need to follow a few key steps. Here’s a general outline of the process:
1. Prepare a backup strategy: Determine the frequency and type of backups you need (e.g., full backups, incremental backups), the retention period for backups, and the storage location for backups. You will need to understand the Recovery-Time-Objective (RTO) and Rcovery-Point-Objective (RPO) at this stage.
2. Snapshot the data: Take a snapshot of your Cassandra data directories. This can be done using the `nodetool snapshot` command. This command creates a hard link of the SSTable files, allowing you to back up the data in a consistent state.
3. Copy the snapshot files: Once the snapshot is complete, copy the snapshot files to a backup location or a remote storage system. You can use tools like `rsync` or `cp` to copy the files. Make sure to preserve the directory structure and file permissions during the copy process.
4. Backup the commit log: Back up the commit log files from the Cassandra data directory. The commit log contains all the write operations that occurred after the last backup, which is essential for data recovery in case of a failure. Copy the commit log files to the backup location as well.
5. Record schema information: It’s crucial to back up the schema information to restore your data correctly. You can use the `nodetool` command with the describecluster or describekeyspace options to obtain the schema details and store them separately.
6. Test your backups: Periodically test your backups to ensure they are valid and can be restored successfully. This practice helps identify any issues with the backup process before an actual data loss event occurs.
7. Consider automated backup tools: Depending on your requirements, you may want to explore automated backup tools specifically designed for Cassandra. These tools can simplify the backup process, provide additional features, and integrate with your backup strategy.
Remember, the exact steps and commands might vary depending on the version of Cassandra you are using and the specific backup strategy you have in mind. Always consult the official documentation and relevant resources for your Cassandra version to ensure accurate backup procedures.
Easily backup and restore your Cassandra cluster with AxonOps
AxonOps provides an enterprise-grade backup & restore solution for your Cassandra clusters as part of the one-stop operations management platform. An enterprise can immediately implement and easily maintain an effective backup & restore process through a highly intuitive UI while ensuring any compliance requirements are quickly addressed. More information can be found here.
Other tools for your Cassandra Backups & Restore
There are also open-source tools for performing backups for your Cassandra clusters, such as Medusa and Esop which will require greater configuration and management though also offer an effective option.
Make your Cassandra data secure, and get started with AxonOps for FREE! You’ll be backing up your Cassandra cluster in minutes.
