You can create volumes to mount Alibaba Cloud disks to a Container Service for Kubernetes (ACK) cluster. You can use the Contain Storage Interface (CSI) plug-in provided by Alibaba Cloud to mount disks by creating persistent volumes (PVs) and persistent volume claims (PVCs). A PV can be statically or dynamically provisioned. This topic describes the features, disk specifications, use scenarios, limits, and billing rules of disk volumes.

Features

Alibaba Cloud disks are block-level data storage resources for Elastic Compute Service (ECS). Alibaba Cloud disks provide low latency, high performance, high durability, and high reliability. Alibaba Cloud disks use a distributed triplicate mechanism to ensure data reliability for ECS instances. If service disruptions occur within a zone due to hardware errors, data in the zone is automatically replicated to an unaffected disk in another zone to ensure data availability.

  • Enhanced SSDs (ESSDs): ESSDs are based on the next-generation distributed block storage architecture and use the 25 Gigabit Ethernet and remote direct memory access (RDMA) technologies. ESSDs provide low-latency input and output. Each ESSD can provide up to 1,000,000 random read/write IOPS. For more information, see ESSDs.

    We recommend that you use ESSDs for scenarios such as online transactional processing (OLTP) databases, NoSQL databases, and Elasticsearch, Logstash, and Kibana (ELK) distributed logs.

  • Standard SSDs: Standard SSDs are high-performance disks that provide consistent high random IOPS and high data reliability.

    We recommend that you use standard SSDs for scenarios such as I/O-intensive applications, small and medium-sized relational databases, and NoSQL databases.

  • Ultra disks: Ultra disks are cost-effective and provide medium random IOPS and high data reliability.

    We recommend that you use ultra disks as system disks for scenarios such as development and testing.

  • Basic disks: Basic disks are the previous generation of disks and are unavailable for purchase.

Disk specifications

The following table describes the performance of disks of different categories.

Category ESSD Standard SSD Ultra disk Basic disk
PL3 PL2 PL1 PL0
Capacity range per disk (GiB) 1261~32768 461~32768 20~32768 40~32768 20~32768 20~32768 5~2000
Maximum IOPS 1000000 100000 50000 10000 25000 5000 Several hundreds
Maximum throughput (MB/s) 4000 750 350 180 300 140 30~40
Formula for calculating the IOPS per disk min{1800 + 50 × Capacity, 1000000} min{1800 + 50 × Capacity, 100000} min{1800 + 50 × Capacity, 50000} min{1800 + 12 × Capacity, 10000} min{1800 + 30 × Capacity, 25000} min{1800 + 8 × Capacity, 5000} N/A
Formula for calculating the throughput per disk (MB/s) min{120 + 0.5 × Capacity, 4000} min{120 + 0.5 × Capacity, 750} min{120 + 0.5 × Capacity, 350} min{100 + 0.25 × Capacity, 180} min{120 + 0.5 × Capacity, 300} min{100 + 0.15 × Capacity, 140} N/A
Average single-channel random write latency in milliseconds (block size = 4 K) 0.2 0.3~0.5 0.5~2 1~3 5~10
API parameter value cloud_essd cloud_ssd cloud_efficiency cloud

For more information about disk performance, see EBS performance.

Scenarios

You can use one of the following methods to mount disks if you want to use the disks to store application data:

Usage notes

  • We recommend that you mount a disk by using a StatefulSet. If you use a Deployment to mount disks, you must set the number of replicated pods to 1. The Deployment cannot guarantee the sequence in which the mounting and unmounting operations are performed. New pods may be launched before the disks are unmounted from the original pods. In this case, the system may fail to mount the disks to the new pods. In addition, due to the update policy of Deployments, the system may fail to mount the disks to the new pods when the pods are restarted. Therefore, we recommend that you do not use a Deployment to mount disks.
  • Make sure that the type of disk matches the ECS instance type that is used in your cluster before you mount a disk. For more information about the matching rules between disk types and ECS instance types, see Instance family.
  • You can mount at most 16 disks to each node. The maximum capacity of each disk is 32 TiB.

Billing method

  • Only pay-as-you-go disks can be mounted. If you change the billing method of an ECS instance in the cluster from pay-as-you-go to subscription, you cannot change the billing method of its disks to subscription. Otherwise, the disks cannot be mounted to the cluster.
  • For more information, visit the ECS product page.
For more information, see Billing methods.