Alibaba Cloud disks are block-level storage resources that you can mount to an ACK cluster as Kubernetes volumes. The Alibaba Cloud Container Storage Interface (CSI) plug-in provisions disk volumes through persistent volumes (PVs) and persistent volume claims (PVCs). Both static and dynamic provisioning are supported.
Disk types
Alibaba Cloud disks fall into four categories. Choose based on your IOPS requirements and workload type.
| Type | Architecture | Max IOPS | Recommended for |
|---|---|---|---|
| Enhanced SSD (ESSD) | Next-generation distributed block storage with 25 Gigabit Ethernet and remote direct memory access (RDMA) | 1,000,000 | Online transactional processing (OLTP) databases, NoSQL databases, ELK (Elasticsearch, Logstash, and Kibana) distributed logs |
| Standard SSD | High-performance disk with consistent random IOPS | — | I/O-intensive applications, small and medium-sized relational databases, NoSQL databases |
| Ultra disk | Cost-effective disk with medium random IOPS | — | Development and testing environments (system disks) |
| Basic disk | Previous-generation disk | — | Unavailable for purchase |
Alibaba Cloud disks provide low latency, high performance, high durability, and high reliability. All disk types use a distributed triplicate mechanism to ensure data reliability for ECS instances. If a service disruption occurs in a zone due to hardware errors, data is automatically replicated to an unaffected disk in another zone.
For detailed performance specifications such as throughput and IOPS limits per disk size, see EBS performance.
Limitations
Review these constraints before provisioning a disk volume.
Workload type
Mount disks using a StatefulSet, not a Deployment. Deployments do not guarantee the order of mount and unmount operations. A new pod may start before the disk is unmounted from the original pod, causing mount failures. If you must use a Deployment, set the replica count to 1.
Node and disk limits
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Each node supports a maximum of 16 mounted disks.
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Each disk has a maximum capacity of 32 TiB.
Disk and instance compatibility
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The disk type must match the Elastic Compute Service (ECS) instance type used in your cluster. For compatibility rules, see Overview of instance families.
Use cases
Mount a disk volume using one of these provisioning approaches:
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Use a statically provisioned disk volume — attach a pre-existing disk by creating a PV manually.
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Use a dynamically provisioned disk volume — let the CSI plug-in provision a disk automatically when a PVC is created.
Billing
Only pay-as-you-go disks can be mounted to an ACK cluster. If you change an ECS instance's billing method from pay-as-you-go to subscription, do not change the attached disk's billing method to subscription — doing so prevents the disk from being mounted to the cluster.
For pricing details, see the ECS product page and Billing.