You can mount disk volumes to serverless Kubernetes (ASK) clusters. This topic describes the features, disk specifications, use scenarios, usage notes, and billing rules of disk volumes.

Features

Alibaba Cloud disks are block-level 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 faults, data in that zone is automatically copied to an unaffected disk in another zone to ensure data availability.

Disks are classified into the following categories based on their performance:
  • Enhanced SSDs (ESSDs): ESSDs are based on the next-generation distributed block storage architecture and utilize the 25 Gigabit Ethernet and remote direct memory access (RDMA) technologies. Each ESSD has low latency and can deliver 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 or 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.

Usage notes

You can mount both statically and dynamically provisioned disk volumes to ASK clusters.

Precautions

  • We recommend that you mount a disk by using a StatefulSet. If you use a Deployment to mount a disk, you must set the number of replicated pods to 1. If the number of replicated pods is not set to 1, multiple nodes may use the disk at the same time when replicated pods are scheduled to different nodes. In this case, you cannot prioritize the node where you want to mount or unmount a disk. When Deployment pods are restarted, disk mounting may fail due to the upgrade policy. Therefore, we recommend that you do not use a Deployment to mount a disk.
  • Before you mount a disk to an ECS instance, make sure that the type of the disk is supported by the ECS instance. Otherwise, the disk cannot be mounted. For more information about the disk types that are supported by different ECS instance types, see Instance families.
  • You can mount at most 16 disks to each node. The maximum capacity of a disk is 32 TiB.

Billing

  • 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.