Disk selection and purchase FAQ

How do I quickly select disk specifications?

Alibaba Cloud offers multiple ESSD specifications. Use the following table to select the product that best suits your business needs.

Key recommendation: If you cannot predict the I/O requirements of your critical systems, or if your workload has significant peaks and troughs, select an ESSD AutoPL disk.

As a new-generation ESSD, it offers the following advantages:

• Decoupled capacity and performance: Capacity and performance can be upgraded independently, unlike previous-generation ESSD PL0/1/2/3 disks where they were coupled.

• Automatic on-demand performance boost: ESSD AutoPL automatically boosts performance in real time based on actual I/O load, preventing disruptions caused by insufficient performance.

What are the product specifications of ESSDs?

ESSDs are available in different performance-based specifications. See ESSDs.

Can I upgrade basic disks (a product from two generations ago) to ESSD series disks?

No. Basic disks cannot be directly upgraded to ESSD series disks because they use different storage architectures. Instead, create a snapshot of the basic disk and use it to create an ESSD series disk.

Can I upgrade previous-generation ultra disks or standard SSDs to ESSD AutoPL disks?

Yes. You can upgrade ultra disks or standard SSDs to ESSD AutoPL disks online by changing the disk type. Disk read and write performance may be slightly affected during the change, but services will not be interrupted and no data will be lost. Perform this operation during off-peak hours.

Previous-generation disks: FAQ about local SSDs

Local SSDs are no longer available. If you still use local SSDs, see Introduction to local SSDs and Local SSD FAQ.

How are ESSDs billed?

ESSDs support the subscription and pay-as-you-go billing methods. For pricing details, see Elastic Block Storage Pricing.

How are separately purchased pay-as-you-go data disks billed?

Pay-as-you-go data disks are billed hourly. If your account balance is insufficient, the service for the pay-as-you-go data disk is suspended.

Can I convert a renewed subscription disk with changed specifications to pay-as-you-go?

No. You must wait until the new subscription period ends, then renew the disk, change its specifications, and convert it to pay-as-you-go.

How to view ESSD AutoPL performance burst usage?

You can view ESSD AutoPL performance burst usage in the ECS console or the EBS console. See View disk monitoring information.

How are the performance metrics and product specifications of ESSDs calculated?

ESSD performance scales linearly with capacity. See ESSDs.

What is the relationship between ESSD performance and instance performance?

For some instance families, storage I/O performance scales linearly with instance type. For example, in the g7se storage-enhanced instance family, a larger instance type provides higher storage IOPS and throughput.

When you create a g7se instance and attach an ESSD:

• If the total ESSD performance does not exceed the instance storage I/O capability, actual storage performance equals the ESSD performance.

• If the total ESSD performance exceeds the instance storage I/O capability, actual storage performance is capped by the instance type.

  For example, an ecs.g7se.xlarge instance has a maximum storage IOPS of 60,000. If you attach a 2 TiB ESSD with a single-disk IOPS of 101,800, the instance IOPS is still capped at 60,000.

For g7se specifications and performance, see Instance families.

What tools can I use to test block storage performance?

Use FIO to test key performance metrics of a raw disk, including IOPS, throughput, and latency. See Test the performance of a block storage device.

Why does my instance go down when I use FIO to test performance?

FIO can test I/O performance on both raw disk partitions and file systems. Testing a raw disk partition directly destroys the file system metadata on that partition, making files inaccessible and potentially crashing the instance. This issue does not occur when testing a file system.

How do I test the performance of an ESSD?

Use FIO to stress test an ESSD. See Benchmark the IOPS of an ESSD.

What is I/O optimization? Can I upgrade an existing ECS instance to an I/O optimized instance?

I/O optimization enhances the data path between an instance and a disk, enabling the instance to achieve the full storage performance of an attached standard SSD.

Yes. Convert a non-I/O optimized instance to an I/O optimized instance by calling ModifyInstanceSpec or ModifyPrepayInstanceSpec.

How does Alibaba Cloud handle resource contention for block storage?

Alibaba Cloud Elastic Block Storage (EBS) is a multitenancy storage service. Disks are available in different categories, such as ESSDs, standard SSDs, and ultra disks. You can purchase different categories for different performance levels, or change performance by resizing a disk or changing its category.

Use CloudMonitor or CloudLens for EBS to monitor disk performance and determine whether your disk type meets your business requirements.

EBS allocates appropriate infrastructure to deliver advertised performance and prevent resource contention. The service is continuously monitored. If a hardware failure or resource contention is detected, Alibaba Cloud reschedules resources or performs maintenance based on the impact.