Elastic Compute Service:FAQ about disk selection and purchase

How do I quickly select disk specifications?

In the era of cloud-native and big data, storage is not just a data carrier but also an engine for business performance. Alibaba Cloud offers multiple specifications of enterprise SSDs (ESSDs). You can use the following table to quickly find 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 business experiences significant peaks and troughs in workload, select an ESSD AutoPL disk.

As a new-generation product in the Alibaba Cloud ESSD series, it offers the following advantages:

• Decoupling of capacity and performance: Capacity and performance can be upgraded independently. This design is more flexible and cost-effective than the previous-generation ESSD PL0/1/2/3 disks, where capacity and performance were coupled.

• Automatic on-demand performance improvement: An ESSD AutoPL disk automatically boosts its performance in real time based on the actual I/O load. This prevents business disruptions caused by insufficient performance.

What are the product specifications of ESSDs?

ESSDs are available in different specifications based on performance. For more information, see ESSDs.

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

No, you cannot. ESSD series disks are built on the latest all-flash storage technology. You cannot directly upgrade basic disks, which are a product from two generations ago, to ESSD series disks. Instead, you must create a snapshot of the basic disk and then use the snapshot to create an ESSD series disk.

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

Yes, you can. You can upgrade previous-generation ultra disks or standard SSDs to ESSD AutoPL disks online by changing the disk type. The upgrade process does not affect your services and is free of charge.

How are ESSDs billed?

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

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.

I have renewed a subscription disk with a specification change. Can I convert it to a pay-as-you-go disk during the new subscription period?

No, you cannot. You must wait until the new subscription period ends. Then, you can renew the disk, change its specifications, and convert it to a pay-as-you-go disk.

How to view ESSD AutoPL performance burst usage?

You can view ESSD AutoPL performance burst usage in the ECS console or the EBS console. For more information, see View disk monitoring information.

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

The performance of an ESSD has a linear relationship with its capacity. A larger capacity provides higher performance. ESSDs offer a significant performance improvement over standard SSDs. For more information, see ESSDs.

What is the relationship between ESSD performance and instance performance?

The storage I/O performance of some instances is linearly proportional to the instance type. For example, the storage I/O performance of the g7se storage-enhanced instance family of Elastic Computing Service (ECS) has a linear relationship with its instance type. For the same instance family, a larger instance type provides higher storage input/output operations per second (IOPS) and throughput.

When you create a g7se instance of a specific type and attach an ESSD:

• If the total performance of the attached ESSDs does not exceed the storage I/O capability of the instance, the actual storage performance is determined by the performance of the ESSDs.

• If the total performance of the attached ESSDs exceeds the storage I/O capability of the instance, the actual storage performance is determined by the storage I/O capability of the instance type.

  For example, you create an ecs.g7se.xlarge instance with 16 GiB of memory. The maximum storage IOPS for this instance is 60,000. If you attach a 2 TiB ESSD with a single-disk IOPS of 101,800, the maximum storage IOPS of the instance is still limited to 60,000. The instance cannot reach the 101,800 IOPS of the 2 TiB ESSD.

For more information about the specifications and performance of the g7se storage-enhanced instance family of ECS, see Instance families.

What tools can I use to test block storage performance?

You can use the open source tool FIO to test key performance metrics of a raw disk. These metrics include input/output operations per second (IOPS), throughput (data transfer rate), and latency (response time). For more information, see Test the performance of a block storage device.

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

The FIO tool can test I/O performance on both raw disk partitions and file systems. If you test a raw disk partition directly, you will destroy the file system metadata on that partition. This makes the files on the partition inaccessible and can even cause the instance to crash. This issue does not occur when you use FIO to test the performance of a file system.

How do I test the performance of an ESSD?

You can use the FIO tool to perform a stress test on an ESSD. For more information, see Test the IOPS performance 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 transfer path between an instance and a disk to ensure that the storage performance of a standard SSD can be fully utilized. This allows an I/O optimized instance to achieve the full storage performance of an attached standard SSD.

Yes, you can. You can convert an existing non-I/O optimized ECS instance to an I/O optimized instance by calling the ModifyInstanceSpec and ModifyPrepayInstanceSpec API operations.

How does Alibaba Cloud handle resource contention for block storage?

Alibaba Cloud Elastic Block Storage (EBS) is a multitenancy storage service. Alibaba Cloud defines performance standards based on different instance types and disk categories. For example, disks are available in different categories, such as ESSDs, standard SSDs, and ultra disks. You can purchase disks from different categories to obtain different levels of performance. You can also change the performance of a disk by resizing it or changing its category.

You can use CloudMonitor or CloudLens for EBS to monitor disk performance data. This helps you determine whether the purchased disk type meets your business requirements. For more information about CloudMonitor and CloudLens for EBS, see Cloud service monitoring and CloudLens for EBS.

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