Production Checklist

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This page provides important recommendations for production deployments of CockroachDB.

Topology

When planning your deployment, it's important to carefully review and choose the topology patterns that best meet your latency and resiliency requirements. This is especially crucial for multi-region deployments.

Also keep in mind some basic topology recommendations:

• Run each node on a separate machine. Since CockroachDB replicates across nodes, running more than one node per machine increases the risk of data loss if a machine fails. Likewise, if a machine has multiple disks or SSDs, run one node with multiple --store flags and not one node per disk. For more details about stores, see Start a Node.

• When starting each node, use the --locality flag to describe the node's location, for example, --locality=region=west,zone=us-west-1. The key-value pairs should be ordered from most to least inclusive, and the keys and order of key-value pairs must be the same on all nodes.

• When deploying in a single availability zone:

  • To be able to tolerate the failure of any 1 node, use at least 3 nodes with the default 3-way replication factor. In this case, if 1 node fails, each range retains 2 of its 3 replicas, a majority.
  • To be able to tolerate 2 simultaneous node failures, use at least 5 nodes and increase the default replication factor for user data to 5. The replication factor for important internal data is 5 by default, so no adjustments are needed for internal data. In this case, if 2 nodes fail at the same time, each range retains 3 of its 5 replicas, a majority.

• When deploying across multiple availability zones:

  • To be able to tolerate the failure of 1 entire AZ in a region, use at least 3 AZs per region and set --locality on each node to spread data evenly across regions and AZs. In this case, if 1 AZ goes offline, the 2 remaining AZs retain a majority of replicas.
  • To ensure that ranges are split evenly across nodes, use the same number of nodes in each AZ. This is to avoid overloading any nodes with excessive resource consumption.

• When deploying across multiple regions:

  • To be able to tolerate the failure of 1 entire region, use at least 3 regions.

Software

We recommend running a glibc-based Linux distribution and Linux kernel version from the last 5 years, such as Ubuntu, Red Hat Enterprise Linux (RHEL), CentOS, or Container-Optimized OS.

Hardware

Sizing

The size of your cluster corresponds to its total number of vCPUs. This number depends holistically on your application requirements: total storage capacity, SQL workload response time, SQL workload concurrency, and database service availability.

Working from your total vCPU count, you should then decide how many vCPUs to allocate to each machine. The larger the nodes (i.e., the more vCPUs on the machine), the fewer nodes will be in your cluster.

Carefully consider the following tradeoffs:

• A smaller number of larger nodes emphasizes cluster stability.

  • Larger nodes tolerate hot spots more effectively than smaller nodes.
  • Queries operating on large data sets may strain network transfers if the data is spread widely over many smaller nodes. Having fewer and larger nodes enables more predictable workload performance.
  • A cluster with fewer nodes may be easier to operate and maintain.

• A larger number of smaller nodes emphasizes resiliency across failure scenarios.

  • The loss of a small node during failure or routine maintenance has a lesser impact on workload response time and concurrency.
  • Having more and smaller nodes allows backup and restore jobs to complete more quickly, since these jobs run in parallel and less data is hosted on each individual node.
  • Recovery from a failed node is faster when data is spread across more nodes. A smaller node will also take a shorter time to rebalance to a steady state.

In general, distribute your total vCPUs into the largest possible nodes and smallest possible cluster that meets your fault tolerance goals.

• Each node should have . For greater stability, we recommend at least 8 vCPUs per node.

• Avoid "burstable" or "shared-core" virtual machines that limit the load on CPU resources.

Basic hardware recommendations

Once you have sized your cluster, derive the amount of RAM, storage capacity, and disk I/O from the number of vCPUs.

This hardware guidance is meant to be platform agnostic and can apply to bare-metal, containerized, and orchestrated deployments. Also see our cloud-specific recommendations.

Before deploying to production, test and tune your hardware setup for your application workload. For example, read-heavy and write-heavy workloads will place different emphases on CPU, RAM, storage, I/O, and network capacity.

Memory

Provision at least 4 GiB of RAM per vCPU for consistency across a variety of workload complexities. The minimum acceptable ratio is 2 GiB of RAM per vCPU, which is only suitable for testing.

• To optimize for the support of large numbers of tables, increase the amount of RAM. For more information, see Quantity of tables and other schema objects. Supporting a large number of rows is a matter of Storage.

• To ensure consistent SQL performance, make sure all nodes have a uniform configuration.

• Disable Linux memory swapping. Over-allocating memory on production machines can lead to unexpected performance issues when pages have to be read back into memory.

• For production deployments, set --cache to 25% or higher. Avoid setting --cache and --max-sql-memory to a combined value of more than 75% of a machine's total RAM. Doing so increases the risk of memory-related failures. For more details, see Cache and SQL memory size.

• Monitor CPU and memory usage. Ensure that they remain within acceptable limits.

Storage

We recommend provisioning volumes with 150 GiB per vCPU. It's fine to have less storage per vCPU if your workload does not have significant capacity needs.

• The maximum recommended storage capacity per node is 2.5 TiB, regardless of the number of vCPUs.

• Use dedicated volumes for the CockroachDB store. Do not share the store volume with any other I/O activity.

• Store CockroachDB log files in a separate volume from the main data store so that logging is not impacted by I/O throttling.

• The recommended Linux filesystems are ext4 and XFS.

• Always keep some of your disk capacity free on production. Doing so accommodates fluctuations in routine database operations and supports continuous data growth.

• Monitor your storage utilization and rate of growth, and take action to add capacity well before you hit the limit.

• New in v21.2: CockroachDB will automatically provision an emergency ballast file at node startup. In the unlikely case that a node runs out of disk space and shuts down, you can delete the ballast file to free up enough space to be able to restart the node.

• Use zone configs to increase the replication factor from 3 (the default) to 5 (across at least 5 nodes).

  This is especially recommended if you are using local disks with no RAID protection rather than a cloud provider's network-attached disks that are often replicated under the hood, because local disks have a greater risk of failure. You can do this for the entire cluster or for specific databases, tables, or rows (Enterprise-only).

Disk I/O

Disks must be able to achieve 500 IOPS and 30 MB/s per vCPU.

• Monitor IOPS using the DB Console and iostat. Ensure that they remain within acceptable values.

• Use sysbench to benchmark IOPS on your cluster. If IOPS decrease, add more nodes to your cluster to increase IOPS.

• Do not use LVM in the I/O path. Dynamically resizing CockroachDB store volumes can result in significant performance degradation. Using LVM snapshots in lieu of CockroachDB backup and restore is also not supported.

• The optimal configuration for striping more than one device is RAID 10. RAID 0 and 1 are also acceptable from a performance perspective.

Node density testing configuration

In a narrowly-scoped test, we were able to successfully store 4.32 TiB of logical data per node. The results of this test may not be applicable to your specific situation; testing with your workload is strongly recommended before using it in a production environment.

These results were achieved using the "bank" workload running on AWS using 6x c5d.4xlarge nodes, each with 5 TiB of gp2 EBS storage.

Results:

Cloud-specific recommendations

Cockroach Labs creates a yearly cloud report focused on evaluating hardware performance. For more information, see the 2022 Cloud Report.

Based on our internal testing, we recommend the following cloud-specific configurations. Before using configurations not recommended here, be sure to test them exhaustively. Also consider the following workload-specific observations:

• For OLTP applications, small instance types may outperform larger instance types.
• Larger, more complex workloads will likely see more consistent performance from instance types with more available memory.
• Unless your workload requires extremely high IOPS or very low storage latency, the most cost-effective volumes are general-purpose rather than high-performance volumes.
  • Because storage cost influences the cost of running a workload much more than instance cost, larger nodes offer a better price-for-performance ratio at the same workload complexity.

AWS

• Use general-purpose m6i or m6a VMs with SSD-backed EBS volumes. For example, Cockroach Labs has used m6i.2xlarge for performance benchmarking. If your workload requires high throughput, use network-optimized m5n instances. To simulate bare-metal deployments, use m5d with SSD Instance Store volumes.

  • m5 and m5a instances, and compute-optimized c5, c5a, and c5n instances, are also acceptable.
  Warning:

  Do not use burstable performance instances, which limit the load on a single core.

• General Purpose SSD gp3 volumes are the most cost-effective storage option. gp3 volumes provide 3,000 IOPS and 125 MiB/s throughput by default. If your deployment requires more IOPS or throughput, per our hardware recommendations, you must provision these separately. Provisioned IOPS SSD-backed (io2) EBS volumes also need to have IOPS provisioned, which can be very expensive.

• A typical deployment will use EC2 together with key pairs, load balancers, and security groups. For an example, see Deploy CockroachDB on AWS EC2.

Azure

• Use general-purpose Dsv5-series and Dasv5-series or memory-optimized Ev5-series and Easv5-series VMs. For example, Cockroach Labs has used Standard_D8s_v5, Standard_D8as_v5, Standard_E8s_v5, and Standard_e8as_v5 for performance benchmarking.

  • Compute-optimized F-series VMs are also acceptable.
  Warning:

  Do not use "burstable" B-series VMs, which limit the load on CPU resources. Also, Cockroach Labs has experienced data corruption issues on A-series VMs and irregular disk performance on D-series VMs, so we recommend avoiding those as well.

• Use Premium Storage or local SSD storage with a Linux filesystem such as ext4 (not the Windows ntfs filesystem). Note that the size of a Premium Storage disk affects its IOPS.

• If you choose local SSD storage, on reboot, the VM can come back with the ntfs filesystem. Be sure your automation monitors for this and reformats the disk to the Linux filesystem you chose initially.

Digital Ocean

• Use any droplets except standard droplets with only 1 GiB of RAM, which is below our minimum requirement. All Digital Ocean droplets use SSD storage.

GCP

• Use general-purpose t2d-standard, n2-standard, or n2d-standard VMs, or use custom VMs. For example, Cockroach Labs has used t2d-standard-8, n2-standard-8, and n2d-standard-8 for performance benchmarking.

  Warning:

  Do not use f1 or g1 shared-core machines, which limit the load on CPU resources.

• Use pd-ssd SSD persistent disks or local SSDs. Note that the IOPS of SSD persistent disks depends both on the disk size and number of vCPUs on the machine.

• nobarrier can be used with SSDs, but only if it has battery-backed write cache. Without one, data can be corrupted in the event of a crash.

  Cockroach Labs conducts most of our internal performance tests using nobarrier to demonstrate the best possible performance, but understand that not all use cases can support this option.

Security

An insecure cluster comes with serious risks:

• Your cluster is open to any client that can access any node's IP addresses.
• Any user, even root, can log in without providing a password.
• Any user, connecting as root, can read or write any data in your cluster.
• There is no network encryption or authentication, and thus no confidentiality.

Therefore, to deploy CockroachDB in production, it is strongly recommended to use TLS certificates to authenticate the identity of nodes and clients and to encrypt in-flight data between nodes and clients. You can use either the built-in cockroach cert commands or openssl commands to generate security certificates for your deployment. Regardless of which option you choose, you'll need the following files:

• A certificate authority (CA) certificate and key, used to sign all of the other certificates.
• A separate certificate and key for each node in your deployment, with the common name node.

• A separate certificate and key for each client and user you want to connect to your nodes, with the common name set to the username. The default user is root.

  Alternatively, CockroachDB supports password authentication, although we typically recommend using client certificates instead.

For more information, see the Security Overview.

Networking

Networking flags

When starting a node, two main flags are used to control its network connections:

• --listen-addr determines which address(es) to listen on for connections from other nodes and clients.
• --advertise-addr determines which address to tell other nodes to use.

The effect depends on how these two flags are used in combination:

Cluster on a single network

When running a cluster on a single network, the setup depends on whether the network is private. In a private network, machines have addresses restricted to the network, not accessible to the public internet. Using these addresses is more secure and usually provides lower latency than public addresses.

Cluster spanning multiple networks

When running a cluster across multiple networks, the setup depends on whether nodes can reach each other across the networks.

Load balancing

Each CockroachDB node is an equally suitable SQL gateway to a cluster, but to ensure client performance and reliability, it's important to use load balancing:

• Performance: Load balancers spread client traffic across nodes. This prevents any one node from being overwhelmed by requests and improves overall cluster performance (queries per second).

• Reliability: Load balancers decouple client health from the health of a single CockroachDB node. To ensure that traffic is not directed to failed nodes or nodes that are not ready to receive requests, load balancers should use CockroachDB's readiness health check.

  Tip:

  With a single load balancer, client connections are resilient to node failure, but the load balancer itself is a point of failure. It's therefore best to make load balancing resilient as well by using multiple load balancing instances, with a mechanism like floating IPs or DNS to select load balancers for clients.

For guidance on load balancing, see the tutorial for your deployment environment:

Connection pooling

Creating the appropriate size pool of connections is critical to gaining maximum performance in an application. Too few connections in the pool will result in high latency as each operation waits for a connection to open up. But adding too many connections to the pool can also result in high latency as each connection thread is being run in parallel by the system. The time it takes for many threads to complete in parallel is typically higher than the time it takes a smaller number of threads to run sequentially.

The total number of workload connections across all connection pools should not exceed 4 times the number of vCPUs in the cluster by a large amount..

For guidance on sizing, validating, and using connection pools with CockroachDB, see Use Connection Pools.

Monitoring and alerting

Despite CockroachDB's various built-in safeguards against failure, it is critical to actively monitor the overall health and performance of a cluster running in production and to create alerting rules that promptly send notifications when there are events that require investigation or intervention.

For details about available monitoring options and the most important events and metrics to alert on, see Monitoring and Alerting.

Clock synchronization

CockroachDB requires moderate levels of clock synchronization to preserve data consistency. For this reason, when a node detects that its clock is out of sync with at least half of the other nodes in the cluster by 80% of the maximum offset allowed, it spontaneously shuts down. This offset defaults to 500ms but can be changed via the --max-offset flag when starting each node.

While serializable consistency is maintained regardless of clock skew, skew outside the configured clock offset bounds can result in violations of single-key linearizability between causally dependent transactions. It's therefore important to prevent clocks from drifting too far by running NTP or other clock synchronization software on each node.

In very rare cases, CockroachDB can momentarily run with a stale clock. This can happen when using vMotion, which can suspend a VM running CockroachDB, migrate it to different hardware, and resume it. This will cause CockroachDB to be out of sync for a short period before it jumps to the correct time. During this window, it would be possible for a client to read stale data and write data derived from stale reads. By enabling the server.clock.forward_jump_check_enabled cluster setting, you can be alerted when the CockroachDB clock jumps forward, indicating it had been running with a stale clock. To protect against this on vMotion, however, use the --clock-device flag to specify a PTP hardware clock for CockroachDB to use when querying the current time. When doing so, you should not enable server.clock.forward_jump_check_enabled because forward jumps will be expected and harmless. For more information on how --clock-device interacts with vMotion, see this blog post.

Considerations

When setting up clock synchronization:

• All nodes in the cluster must be synced to the same time source, or to different sources that implement leap second smearing in the same way. For example, Google and Amazon have time sources that are compatible with each other (they implement leap second smearing in the same way), but are incompatible with the default NTP pool (which does not implement leap second smearing).
• For nodes running in AWS, we recommend Amazon Time Sync Service. For nodes running in GCP, we recommend Google's internal NTP service. For nodes running elsewhere, we recommend Google Public NTP. Note that the Google and Amazon time services can be mixed with each other, but they cannot be mixed with other time services (unless you have verified leap second behavior). Either all of your nodes should use the Google and Amazon services, or none of them should.
• If you do not want to use the Google or Amazon time sources, you can use chrony and enable client-side leap smearing, unless the time source you're using already does server-side smearing. In most cases, we recommend the Google Public NTP time source because it handles smearing the leap second. If you use a different NTP time source that doesn't smear the leap second, you must configure client-side smearing manually and do so in the same way on each machine.
• Do not run more than one clock sync service on VMs where cockroach is running.
• For new clusters using the multi-region SQL abstractions, Cockroach Labs recommends lowering the --max-offset setting to 250ms. This setting is especially helpful for lowering the write latency of global tables. For existing clusters, changing the setting will require restarting all of the nodes in your cluster at the same time; it cannot be done with a rolling restart.

Tutorials

For guidance on synchronizing clocks, see the tutorial for your deployment environment:

Cache and SQL memory size

CockroachDB manages its own memory caches, independently of the operating system. These are configured via the --cache and --max-sql-memory flags.

Each node has a default cache size of 128MiB that is passively consumed. The default was chosen to facilitate development and testing, where users are likely to run multiple CockroachDB nodes on a single machine. Increasing the cache size will generally improve the node's read performance.

Each node has a default SQL memory size of 25%. This memory is used as-needed by active operations to store temporary data for SQL queries.

• Increasing a node's cache size will improve the node's read performance.

• Increasing a node's SQL memory size will increase the number of simultaneous client connections it allows, as well as the node's capacity for in-memory processing of rows when using ORDER BY, GROUP BY, DISTINCT, joins, and window functions.

  Note:

  SQL memory size applies a limit globally to all sessions at any point in time. Certain disk-spilling operations also respect a memory limit that applies locally to a single operation within a single query. This limit is configured via a separate cluster setting. For details, see Disk-spilling operations.

To manually increase a node's cache size and SQL memory size, start the node using the --cache and --max-sql-memory flags. As long as all machines are provisioned with sufficient RAM, you can experiment with increasing each value up to 35%.

$ cockroach start --cache=.35 --max-sql-memory=.35 {other start flags}

Dependencies

The CockroachDB binary for Linux depends on the following libraries:

These libraries are found by default on nearly all Linux distributions, with Alpine as the notable exception, but it's nevertheless important to confirm that they are installed and kept up-to-date. For the time zone data in particular, it's important for all nodes to have the same version; when updating the library, do so as quickly as possible across all nodes.

File descriptors limit

CockroachDB can use a large number of open file descriptors, often more than is available by default. Therefore, please note the following recommendations.

For each CockroachDB node:

• At a minimum, the file descriptors limit must be 1956 (1700 per store plus 256 for networking). If the limit is below this threshold, the node will not start.
• It is recommended to set the file descriptors limit to unlimited; otherwise, the recommended limit is at least 15000 (10000 per store plus 5000 for networking). This higher limit ensures performance and accommodates cluster growth.
• When the file descriptors limit is not high enough to allocate the recommended amounts, CockroachDB allocates 10000 per store and the rest for networking; if this would result in networking getting less than 256, CockroachDB instead allocates 256 for networking and evenly splits the rest across stores.

Increase the file descriptors limit

Attributions

This section, "File Descriptors Limit", is in part derivative of the chapter Open File Limits From the Riak LV 2.1.4 documentation, used under Creative Commons Attribution 3.0 Unported License.

Orchestration / Kubernetes

When running CockroachDB on Kubernetes, making the following minimal customizations will result in better, more reliable performance:

• Use SSDs instead of traditional HDDs.
• Configure CPU and memory resource requests and limits.

For more information and additional customization suggestions, see our full detailed guide to CockroachDB Performance on Kubernetes.

Transaction retries

When several transactions try to modify the same underlying data concurrently, they may experience contention that leads to transaction retries. To avoid failures in production, your application should be engineered to handle transaction retries using client-side retry handling.

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