You can mount disk volumes to ACK Serverless 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 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 types
Item | ESSD AutoPL disk | ESSD | Standard SSD | Ultra disk | Basic disk | |||
PL3 | PL2 | PL1 | PL0 | |||||
Capacity range per disk (GiB) | 40~65,536 | 1261~65,536 | 461~65,536 | 20~65,536 | 20~65,536 | 20~32,768 | 20~32,768 | 5~2,000 |
Maximum IOPS | 1,000,000 | 1,000,000 | 100,000 | 50,000 | 10,000 | 25,000 | 5,000 | Several hundreds |
Maximum throughput (MB/s) | 4,096 | 4,000 | 750 | 350 | 180 | 300 | 140 | 30~40 |
Formula for calculating the IOPS per disk |
| min{1,800 + 50 × Capacity, 1,000,000} | min{1,800 + 50 × Capacity, 100,000} | min{1,800 + 50 × Capacity, 50,000} | min{1,800+12 × Capacity, 10,000} | min{1,800 + 30 × Capacity, 25,000} | min{1,800 + 8 × Capacity, 5,000} | None |
Formula for calculating the throughput per disk (MB/s) |
| min{120 + 0.5 × Capacity, 4,000} | 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} | None |
Average one-way random write latency in milliseconds (block size = 4 KB) | 0.2 | 0.2 | 0.2 | 0.2 | 0.3~0.5 | 0.5~2 | 1~3 | 5~10 |
API parameter value | cloud_auto | cloud_essd | cloud_essd | cloud_essd | cloud_essd | cloud_ssd | cloud_efficiency | cloud |
For more information about disk performance, see Block storage performance.
Usage notes
You can mount both statically and dynamically provisioned disk volumes to ACK Serverless clusters.
For more information about how to mount a statically provisioned disk volume, see Statically provision disks.
For more information about how to mount a dynamically provisioned disk volume, see Dynamically provision a disk volume by using the CLI or Use a dynamically provisioned disk volume in the console.
Usage notes
Alibaba Cloud disks cannot be shared. Each disk can be mounted only to one pod.
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.
The type of disk must match the ECS instance types that are used in your cluster before you can mount a disk. For more information about the matching rules between disk types and ECS instance types, see Instance families.
You can mount at most 16 disks to each node. The maximum capacity of each disk is 32 TiB.
When you mount a disk volume, if the securityContext.fsgroup parameter is set in the application template, kubelet performs the
chmodandchownoperations after the volume is mounted. This increases the mounting time. For more information about how to reduce the mounting time, see Why does it require a long time to mount a NAS volume? and Why does it require a long period of time to mount an OSS volume?.
Billing rules
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 information about the billable items of disks, see EBS billing. For more information about the pricing of disks, visit the ECS product page.
If the disk that you want to mount does not support the subscription billing method, you can purchase storage capacity units (SCUs) to reduce the cost. For more information about SCUs, see Introduction to SCUs.
For more information, see Billing.