1. All the examples available are showing Redis cluster being deployed as a combination of Kubernetes’ StatefulSets and PersistentVolumes. This process requires users to familiarize themselves with various k8s resource objects, learn many MySQL operation details and maintain a set of complex management scripts. Stable unique network identifiers. yaml 392 kubectl apply -f pod2. This allows you to easily replicate Pods and attach a storage volume to the Pods. Within each pod, is there any way (through environment variable injection or similar) for us to get a unique identifier that. 3343 Perimeter Hill Drive. Step 1 - Create Kubernetes Environment. This page describes the use of StatefulSet objects in Google Kubernetes Engine (GKE). The StatefulSet guarantees that a given network identity will always map to the same storage identity. Kubernetes Deployments Vs StatefulSets. Deployment is a resource to deploy a stateless application, if using a PVC, all replicas will be using the same Volume and none of it will have its own state. Unlike Deployments or StatefulSets, which manage the deployment of Pods on a per-replica basis, DaemonSets manage the deployment of Pods on a per-node basis. When a StatefulSet's . A StatefulSet can deploy applications that need to reliably identify specific replicas, rollout updates in a pre-defined order, or. 0 API compatibility in Amazon DocumentDB. 1 Answer. The example in this blog deploys on Centos7 using kubeadm. Authors: Ravi Gudimetla (Apple), Filip Křepinský (Red Hat), Maciej Szulik (Red Hat) This blog describes the two features namely minReadySeconds for StatefulSets and maxSurge for DaemonSets that SIG Apps is happy to graduate to stable in Kubernetes 1. g. Un StatefulSet es el objeto de la API workload que se usa para gestionar aplicaciones con estado. The database and Kubernetes itself run on the same machines. There is confusion amongst Kubernetes users as to when one should make a Deployment with a PVC and when they should use a StatefulSet with a PVC. Apr 16, 2020 at 6:14. In general you cannot convert a StatefulSet into a Deployment unless you only plan on. StatefulSetの概要. Get Started. $ kubectl create ns redis $ kubectl apply -f redis-service. Kubernetes (K8s)is an open-source container orchestration system. spec: rules: - paths: - path: /app-redis-0 backend: serviceName: redis. Now let’s talk about StatefulSets. Uses ReplicaSets for scaling and updates. To make it easier to eliminate fields or restructure resource representations, Kubernetes supports multiple API versions, each at a different API path, such as /api/v1 or /apis/extensions/v1beta1 and to extend the Kubernetes API, API groups is implemented. Deployment. . By far the most common way to run a database, StatefulSets is a feature fully supported as of the Kubernetes 1. February 11, 2023 by jamezshame. Statefulsets is used for Stateful applications, each replica of the pod will have its own state, and will be using its own Volume. StatefulSet est l'objet de l'API de charge de travail utilisé pour gérer des applications avec état (stateful). yaml pod2. It can manage the scaling and deployment of a collection of. StatefulSets(since Kubernetes 1. Conclusion. Step 2. Some instructions on what kubeadm provides and how to deploy a Kubernetes cluster is. This blog post will discuss how this feature can be used. ReplicaSet vs. I'm trying to deploy Solr Cloud into Kubernetes using StatefulSets. There were no major changes to the API Object, other than the community selected name, but we added the semantics of “at most one. When the Grafana deployment becomes unstable due to crash looping, bugs, and so on, you can roll back a deployment to an earlier version (a REVISION). Parallel pod management tells the StatefulSet controller to launch or terminate all Pods in parallel, and not to wait for Pods to become Running and Ready or completely terminated prior to launching or terminating another Pod. I have a cluster on gke with apache, mysql and keyrock and i would like to scale it up with horizontal pod autoscaler. If your application doesn't require any of these, you should deploy your application using a Deployment. Why not to use the Statefulsets for stateless applications in Kubernetes ? As Stateful sets have the same capabilities as Deployment PVC, HPA, and others. 26 introduced a new, alpha-level feature for StatefulSets that controls the ordinal numbering of Pod replicas. Kubernetes Deployments vs StatefulSets (7 answers) Closed 2 years ago . Kubernetes Statefulsets are used to deploy Stateful Applications. Statefulsets is used for Stateful applications, each replica of the pod will have its own state, and will be using its own Volume. Apr 6, 2020 at 8:53. Our current updateStrategy is. For stateless applications, using Deployment objects is most suitable. It is similar to Deployment, but Statefulsets requires a Service Name . StatefulSet. PVCs are not the only reason to use Statefulsets over Deployments. Deployment. StatefulSet: Key Differences. Kubernetes Replication Controller vs Deployment Deployments are intended to replace Replication Controllers. Let's be friends: Explore managing stateful applications with Kubernetes StatefulSets — when to use them, how to deploy MongoDB. . Ordinals can start from arbitrary non-negative numbers. DaemonSet vs. To summarize, we changed db Deployment into a StatefulSet, we added a command that creates MongoDB. Represents the latest available observations of a statefulset’s current state. The volumeClaimTemplates automatically creates a new PersistentVolumeClaim each time a pod is replicated. Deployment Vs Stateful sets. The domain managed by this Service. one replica pod will go down and the updated pod will come up. Remember that you can choose any namespace of your choice here. Each new pod in statefulset then have a new PV attached to. As a result, running this example will require an environment based on Kubernetes 1. 2. In this article. If you need to use deployment instead of statefulset, just add kind: Deployment to the nodeSpecs. support@dzone. Network Identities: Kubernetes. Users can deploy and maintain a set of highly available MySQL services in k8s based on StatefulSets, the process is relatively complex. StatefulSets. OK, so back to Deployment with PVC or StatefulSet with PVC. 3. Switch on the feature gate with the command line flag --feature-gates=StatefulSetMinReadySeconds=true on kube-apiserver and kube-controller-manager. There seems to be a recurring bad practice among the charts in this repository: using a Deployment to manage pods using Persistent Volume Claims, rather than the proper StatefulSet. StatefulSet est l'objet de l'API de charge de travail utilisé pour gérer des applications avec état (stateful). To help deploy Pods, Kubernetes provides three different options: Deployments, DaemonSets, and StatefulSets. StatefulSets ensure stable network identities and ordered pod deployment/termination, which is crucial for maintaining data integrity. Modelling Stability with StatefulSets. : Using StatefulSets. The diagram below shows how Deployment and StatefulSets assign names to the Pods. Kubernetes is a dynamic platform where objects are usually created in parallel and with random names. You can only delete or scale up/down the Statefulset. StatefulSets manage the deployment and scaling of a set of Pods, and provides guarantees about the ordering and uniqueness of these Pods. 80 383 more pod1. Kubernetes provides Deployments for managing application orchestration. io/v1beta1 metadata: name: deployer. Check the status of the Deployment using the kubectl get deployments command. The StatefulSets are mostly used for deploying Stateful applications where we require a unique network identifier or Storage. There is a separate controller. The helm docco provides a Job example run post-install via annotations. Like a Deployment, a StatefulSet manages Pods. On the other hand, Jenkins is a stateful application. This is essential. Their replicas are not identical as each one needs its own identity and storage. HPA is a Kubernetes component that automatically updates workload resources such as Deployments and StatefulSets, scaling them to match demand for applications in the cluster. It allows us to automate deployments, scale, and manage containerized applications. To update the deployment, modify the YAML file and run the same command again. apps "web" created. This deployment mode is the easiest way to deploy Loki at scale. Although Kubernetes is best known for running applications, it's also capable of running databases. Pod Management. My Kubernetes Workspace. Contrairement à un Deployment, un. Of course, the scaling depends on the app you are deploying. . 2. This appears to work : kubectl delete statefulsets mariadb -n openstack --force --grace-period=0 --cascade=false. In this documentation you will learn how HPA works, how to use it, what is supported etc. Comme un Déploiement, un StatefulSet gère des Pods qui sont basés sur une même spécification de conteneur. It allows you to define the Kubernetes Deployment or StatefulSet that you want KEDA to scale based on a scale trigger. kubectl delete -f <file. Statefulsets. Stable, unique network identifiers. Kubernetes StatefulSet vs. StatefulSets Example Step 1 - Create Kube Environment. Deployment vs. Because Elasticsearch client nodes are stateless, you can deploy them as Kubernetes Deployments. Configuring the YAML for a DeploymentStatefulSet vs Deployment. You can deploy Elasticsearch master nodes as Kubernetes Deployments or StatefulSets. Deployments are a great choice for applications that don’t require any state to be maintained. Stable And Ordered. yaml. Ordered, graceful deployment and scaling. Pods hold the containers for an application. As opposed to the Deployment, the StatefulSet creates pods directly. Deployment is a resource to deploy a stateless application, if using a PVC, all replicas will be using the same Volume and none of it will have its own state. KEDA will monitor that service and based on the events that occur it will automatically scale. StatefulSets are Kubernetes resources that allow us to deploy and manage the stateful application. If you want to provide workload persistence using Kubernetes persistent storage, you can incorporate a StatefulSet into your solution. Statefulset vs. To provision a static PV for a Deployment workload, the procedure is as follows: Note: The examples in this section. 4. 5 Post deployment tasks; 8. As the world becomes increasingly digital, companies are turning to cloud-based solutions like Kubernetes to help manage their applications. StatefulSets Example. They have different semantics while updating or when the pod. Nota: Los StatefulSets son estables (GA) en la versión 1. Normally a pod would get a new name if it is killed and respawned by Kubernetes, but if it is managed by a Statefulset it respawns with the same name. In the previous blog we created a stateless application, deployed with K8s resource Deployment, which allows one to replicate the application, but where data is lost when Pods are restarted, meaning there were no data consistency. Skaffold is a command line tool from Google that brings automation to the deployment workflow of Kubernetes applications. Pods deployed by Deployment are identical and interchangeable, created in random order with random hashes in their Pod names. StatefulSet:. Two of the most commonly used resources are Kubernetes Deployment and Kubernetes StatefulSet. You can also learn how to Deploy a stateful application. Pods (and, by extension, containers) are, nevertheless, short-lived entities. In this video, we cover Kubernetes Statefulsets in detail. Pods (and, by extension, containers) are, nevertheless, short-lived entities. Deployment is best suited for stateless applications while StatefulSet is best suited for stateful applications. kind: Service metadata: name: redis labels: app: redis spec: type: ClusterIP ports: - name: redis port: 6379 targetPort. 所有pod共享存储 3. We will use Redis as Statefulsets for our Vote application. Gestiona el despliegue y escalado de un conjunto de Pods, y garantiza el orden y unicidad de dichos Pods. Given this difference, Deployment is more suited to work with stateless applications. StatefulSets is a new feature implemented in Kubernetes 1. In this article, we will focus on how to deploy a PostgreSQL database on a Kubernetes cluster using StatefulSets. and data from the image is copied to only one PVC where are rest two pods. Both Deployment and StatefulSet try to maximize the availability - but StatefulSet cannot sacrifice data consistency (e. Kubernetes Deployment vs. As the Kubernetes manual states: StatefulSets are valuable for applications that require one or more of the following: Stable, unique network identifiers. Kubernetes Statefulsets are used to deploy Stateful Applications. Here is a step by step tutorial on how to use StatefulSets and some basic operations on StatefulSets. Kubernetes DaemonSet is a great way to manage and deploy applications in a clustered environment. 0 with new features and enhancements is available now. Fully managed. It allows us to automate deployments,. The primary idea behind StatefulSets is to allow developers to deploy applications that require data to be stored in a filesystem with the ability to re-attach to them if they restart by failure. be/ha3LjlD6g7g In this Kubernetes. Currently there are several API groups in use:A StatefulSets provides a persistent identity to the pods that they create and manage. It is a Kubernetes resource, to manage stateful applications. 那使用Deployments更重要的是，可以方便Rollback到之前版本，而使用StatefulSets、DaemonSets. 5; it consists of a bond between the pod and the Persistent Volume. Requirements of Stateful Applications. You make sure to bind a volume to your database container. Configuring the YAML for a Deployment StatefulSet vs Deployment. 那使用Deployments更重要的是，可以方便Rollback到之前版本，而使用StatefulSets、DaemonSets. Its just not worth the risk to see if your app supports concurrent writes, so dont guess. You should delete the deployment and then create new statefulset. kubectl get pods NAME READY. Kubernetes StatefulSet is the workload API object used to manage stateful applications. Share. After kubernetes 1. Additional note: PVCs created by StatefulSets won't be deleted when deleting the StatefulSet as resource. Ordered, automated rolling updates. 6. Kubernetes Deployment vs. Editor’s note: this post is part of a series of in-depth articles on what's new in Kubernetes 1. If you are unsure about whether. Deployment. If there's heavy load, you can set up a HorizontalPodAutoscaler to. Unlike a. I'm using Logstash on Kubernetes and use the official Helm chart at this link. In these circumstances you may have to reach for alternative deployment. No guarantee of unique network identities or persistent storage. Let's be friends: Explore managing stateful applications with Kubernetes StatefulSets — when to use them, how to deploy MongoDB. Ordered Deployment and Scaling. Kubernetes is an open-source orchestration system for automating deployment, scaling, and management of containerized applications. We set up and ran MongoDB as a StatefulSet, and examined the limitations and best practices while implementing StatefulSets. kubectl create -f statefulset. In contrast to that, the Pods deployed by StatefulSet component are NOT identical and deployment is more complex. Suppose you see the pods using the kubectl get pods command. There are two primary options for deploying a database on Kubernetes: StatefulSets and. This is called dynamic provisioning, which allows StatefulSets to create storage volumes on-demand,. StatefulSetは状態を保持する (ステートフルな)アプリケーションを管理するためのKubernetesオブジェクトだ。. Kubernetes StatefulSets provide two main advantages (for stateful applications) over Deployments: a stable identity of the pods and the ability to follow specific Deployment orders. StatefulSets + Operators. The same thing can be done by using StatefulSets. By default, statefulsets start the first, then second, then third, etc. Deployments - Semaphore 24 May 2023 · Software Engineering Understanding ReplicaSet vs. Not all stateful applications scale nicely. Kubernetes Deployments vs StatefulSets. It makes sense for Operators to rely on them and benefit from the pod volume mapping handled by Kubernetes. Open this file in a code-editor and write the following code into it: apiVersion: apps/v1. Additionally, we are creating a Persistent Volume using the volumeClaimTemplate and using it in the StatefulSet to store the PostgreSQL data. StatefulSets handle the deployment and scaling of sets of Kubernetes pods, providing guarantees about their uniqueness and ordering. 9) is a Kubernetes resource used to manage stateful applications. Here, in this example we are deploying a standalone. 而因為有關聯，所以在Deployment下的Label Name，會同樣印在pod上。. In the last lesson, we skipped over the whys and wherefores of StatefulSets to focus on implementing Secrets. When you update the Pod template in a StatefulSet, the controller recreates the Pods with the updated template. Just to avoid data corruption if you are changing the replica to more then one. They manage pods by assigning persistent identities for rescheduling and storage assignments, ensuring that pods always get the same unique ID and volume attachment when scheduled to another node. If you need the pods that make up your application to have consistent, and predictable hostnames, then use. StatefulSet represents a set of pods with consistent identities. StatefulSet. 2. StatefulSet Kubernetes | Understand what StatefulSet in Kubernetes is and how it works Using StatefulSet in practice 🙅🏼♀️ youtu. See moreTL;DR. Here is a step by step tutorial on how to use StatefulSets and some basic operations on StatefulSets. Replicas in a StatefulSet follow a graceful, sequential approach to deployment, scale, upgrades, and terminations. Introducing Client-Side Field Level Encryption and MongoDB 5. Deploy it using the command below: $ kubectl apply -n test-namespace -f deployment. Deploying a. 1 Answer. StatefulSets are Kubernetes component that is used specifically for stateful applications. Since we specified replica count of 3, three pods will be. Ésta publicación muestra tres formas diferentes de implementar una aplicación en pods de Kubernetes. Ésta publicación muestra tres formas diferentes de implementar una aplicación en pods de Kubernetes. With StatefulSets, you can deploy and manage your stateful applications on Kubernetes with confidence, knowing that they’re being managed in a way that’s familiar and intuitive. How PVC works in case of statefulsets. What are StatefulSets and why are they needed? Deployments vs StatefulSets TL;DR. Their hostnames include their numerical replica identifier, allowing external applications to interact with the same replica after a Pod’s rescheduled. With the clean service created, proceed to deploy it as shown below. Statefulsets are used for databases where the state of the application is the crucial part of the deployment. Pods are a great way for you to deploy an application, but there is some limitation to the pod resource type. Kubernetes deployments manage stateless services running on your cluster (as opposed to for example StatefulSets which manage stateful services). When a PVC or volumeClaimTemplate is requested, Kubernetes chooses an available PV in the system and allocates it to the Deployment or StatefulSets workload. Case of statefulsets: name of pod initially: mongo-0 name of pod after it gets deleted & recreated: mongo-0 Here, pod name remained the same. You may notice two things here: (1) there is only one pod created while we asked for three, and (2) the pod name contains the StatefulSet name. This article is the fourth in a series using infrastructure as code to deploy applications with Kubernetes. Download and install a kubectl greater than v1. A. The kubectl apply -f used to apply the configuration file kubernetes (where your deploy your desired application). First, let's verify that StatefulSet has created the leader ( mehdb-0) and. Does it need ordered instance scale-up and scale-down? If you share what application you are using, it is easier to tell if it tolerate that the instances scale-up or. Suppose your deployment configuration file looks like this and you saved that in nginx. A StatefulSet is better suited to stateful workloads that require persistent storage on each cluster node, such as databases and other identity-sensitive workloads. Pricing. This tutorial shows you how to run Apache Cassandra on Kubernetes. You may need to delete the associated headless service separately after the StatefulSet. Stable, persistent storage. yaml. Free Forever plan: 10,000 series metrics;. Stable Network Identities: StatefulSets provide stable network identities for each pod, making it easy to communicate with specific pods in the set. Al igual que un Deployment, un StatefulSet gestiona Pods que se basan en una especificación idéntica de contenedor. deployment vs. In statefulsets each replica pod created has an index number starting from 0 and it will only setup the next replica if the previous one is running. Statefulset is a Kubernetes resource that handles pods that you need to hold a state. yaml file first, so that even if our pod restarts or gets deleted, our data won. 3 Updating a StatefulSet. They both consume resources and can affect overall performance. Instead you create Deployments and StatefulSets where a controller takes care of that. As such, stateless applications are easier to scale as well,. As far as a Deployment is concerned, Pods are interchangeable. A number of features intrinsic with the use of StatefulSets are the guarantees around deployment and scaling. Hint: It starts at FREE. podManagementPolicy: "Parallel". It dictates the needs of dedicated volumes, unique hostname records, and a specific order of deployment. We want to deploy service sets to machine "areas" so that services are running close to resources they manage. This article describes how to create, update, and delete StatefulSets, which are used to maintain the state of an application beyond a pod lifecycle in an Azure Kubernetes Serice deployment in AKS hybrid. Scaling a StatefulSet refers to increasing or decreasing the number of replicas. Thus, you have one SQL Server instance deployed per pod in the Kubernetes cluster. This tool is tailored to provide developers with an experience of iteration…The containers in a pod talk to each other via local host, whereas pod-to-pod communication is done via services. This can be done by updating the value of an annotation within the pod template. currently we scaled one of our statefulsets to have 11 replicas. headless service is necessary to create a stable DNS name for each pod. StatefulSet (stable-GA in k8s v1. Similar to deployments, StatefulSets manage pods with identical container specifications. StatefulSets are created in a similar way to Deployment objects. As of Kubernetes v1. 1 Answer. service都有ClusterIP,可以负载均衡 StatefulSet适合场景有状态的应用特点1. This sticky characteristic makes it possible to run databases on. You cannot manage to use ReadWriteOnce with deployment because it cannot scale. statefulSet {. I didn't really talk about (3) and (4) but that can also help with clusters as you can tell the first one to deploy to become the master and the next one find the first and treat it as master, etc. StatefulSets and DaemonSets. I think statefulsets make sense for it. The below example demonstrates the components of a StatefulSet. I have chosen this option since we are using a single node MariaDB, which works better as a statefulset than as a deployment. In addition to declarative scaling, StatefulSets also provide declarative updates, similar to Deployments. Statefulsets only provide a way to have unique naming e. Like a Deployment, a StatefulSet manages Pods that are based on an identical container spec. Deployments and StatefulSets are the most common way to scale workloads with KEDA. in general you should refer to the "Using StatefulSets" in. Ordered, graceful deployment and scaling. TL;DR. The solution(s) : Use a StatefulSet, ReplicaSet or DaemonSet to ensure the Pod creation after a Node failure. Stateful Applications in Kubernetes. We will create the “ redis ” namespace then apply the file. You can also learn how to Deploy a stateful application. Overview. @billimek it feels like a similar conversation happened on the original helm repo, so I'm not able to find it there. Restarting a Rollout. Statefulsets use a volumeClaimTemplates array. Comme un Déploiement, un StatefulSet gère des Pods qui sont basés sur une même spécification. In this tutorial, we will discuss two different ways to deploy our containerized application on Kubernetes using Deployment and StatefulSets resources. Using volumeClaimTemplates, each replica will get a unique PersistentVolumeClaim with statefulset whereas all replicas would share the PersistentVolumeClaim with a deployment. They both have self-healing. StatefulSets and DaemonSets. Using a statefulset also ensures that pods. A StatefulSet is a group of pods with persistent identities and stable hostnames, designed to run stateful and replicated Kubernetes services. kubectl delete statefulsets <statefulset-name>. StatefulSet vs. StatefulSets are particularly useful when you have stateful applications, such as databases, that require stable network identities and persistent storage. The support for autoscaling the statefulsets using HPA is added in kubernetes 1. Statefulsets and Operators are not that similar. This tutorial will demonstrate Kubernetes StatefulSets as well as PodDisruptionBudgets, and PodAntiAffinity. Pods hold the containers for an application. upgrades/terminations are done sequentially from the pod with the biggest index number to the pod with index number 0. To create a service, use the kubectl expose command. More info about statefulsets. 6 StatefulSet vs Deployment: persistent storage; 8. Other examples of stateful applications include MySQL clusters, Redis, Kafka, MongoDB, and others. StatefulSets. Watch the presentation below given by Ali Kahoot, DevOps Engineer & Trainer at Tarabut Gateway. Key differences. (I don't use mine to create the deployment, just to patch the image tag) kind: ClusterRole apiVersion: rbac. Stateful applications are those which required persistent storage to work aptly. 3343 Perimeter Hill Drive. OF THE TALKKubernetes provides different resources for deploying applications, we will be lookin. 5. Deployment. First of all Headless services are vaguely used to access all the pod replicas directly instead of using the Services. There are other kinds of workload too, such as DaemonSets and StatefulSets. We'll use Jenkins as the first application we'll deploy. They are listed below. OpenShift deployment is a replication controller based on a user-defined template called a deployment configuration. Each Pod in the StatefulSet can access local persistent volumes that stick to it even after it's rescheduled. All the examples available are showing Redis cluster being deployed as a combination of Kubernetes’ StatefulSets and PersistentVolumes. summary, it is possible to set min / max replicas for a statefulset using HPA. 1 What is a StatefulSet? 8. 7) uses an update strategy to configure and disable. You should not run a database (or other stateful workload) as Deployment, use StatefulSet for those. An example of a stateful application is a database or key-value store to which data is saved and retrieved by other. StatefulSet(stable-GA in k8s v1. Create a StatefulSet file. Pods in a StatefulSet will have an IP. This page describes the use of StatefulSet objects in Google Kubernetes Engine (GKE). (This article is part of our Kubernetes Guide. The problem is : a Pod will not be re-created after the Node failure (like a reboot). Additionally, StatefulSets enables you to reschedule database pods to other nodes. Using the Kubernetes Scheduler, the Deployment Controller runs replicas on any available node with available resources. Let’s summarize the key differences between Deployments, StatefulSets, and DaemonSets: Deployments: Designed for stateless applications. #Deployment vs. StatefulSets are used for deploying stateful applications that require stable network identities and persistent data. 8. Today, we’ll take a look at some of the same YAML markup, but zero in on StatefulSets instead. It is generated by hashing the PodTemplate of the ReplicaSet and using the resulting hash as the label value that is. Author: Peter Schuurman (Google) Kubernetes v1. The StatefulSet controller uses this field as a collision avoidance mechanism when it needs to create the name for the newest ControllerRevision. Create Some Data. StatefulSets. Very useful for HA workloads. Nashville, TN 37211. If you are using Deployment, StatefulSet, DaemonSet, ReplicaSet or ReplicationController, to trigger a new deployment you will need to make a manual change to the pod template component of the configuration defined by the resource. StatefulSets make it easier to. If we deploy the statefulset from scratch, Kubernetes starts them one after another. However, even when using the same name for the volume claim as before, it seems to be creating an. Deployments allow you to define the lifecycle of applications, including the container images they use, the number of pods and the manner of updating them. Deploy the Java service to Amazon EKS. Stable, persistent storage. StatefulSets can be used to create pods with a guaranteed start-up order and unique identifiers.