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Shared block storage FAQ

How to apply for public test qualification?

Shared block storage is currently under public trial, and you need to apply for a trial.

What is shared block storage?

ECS shared block storage is a block-level storage device that supports concurrent read and write access of multiple ECS instances. It has the characteristics of multiple concurrency, high performance and high reliability. A single block shared block storage supports mounting to up to 8 ECS instances at the same time.

To mount shared block storage, please refer to video mount shared block storage to multiple ECS instances.

Why do I need to share block storage?

In the traditional cluster architecture, multiple computing nodes need to be able to access the same data to prevent business interruption when one or more computing nodes fail, and to ensure that the whole highly available cluster can provide business services continuously.

Therefore, important data files need to be placed on shared block storage and managed uniformly through the cluster file system. When multiple computing nodes in the front end access to read and write concurrently, the consistency of data among multiple nodes is maintained.

What industry and business scenarios does shared block storage apply to?

Shared block storage products are designed for high availability architecture of core business of enterprise customers, and are suitable for shared access scenarios of block storage devices under shared-everything architecture, such as Oracle RAC database high availability architecture commonly used by government, enterprise and financial industry, and server High-availability cluster high availability architecture.

How to use shared block storage correctly?

The shared block storage product itself does not provide a cluster file system, so you need to install the cluster file system to manage the shared block storage.

If you only mount shared block storage to multiple ECS instances, but still use a regular file system to manage it, it will cause disk space allocation conflicts and data file inconsistencies, as shown below:

Disk space allocation conflict

If a shared block storage is mounted to multiple instances, when instance An is writing a file, it will query the file system and available disk space. After the file is written, it will modify the space allocation record on instance A, but will not modify the records of other instances. Therefore, when instance B writes to a file, the disk space already allocated by instance A may be re-peeled, resulting in a disk space allocation conflict.

Data files are inconsistent

When instance A reads the data and records it in the cache, another process on instance An accesses the same data and reads it directly from the cache. However, if instance B modifies the same data at this time, but instance A does not know it and still reads the data from the cache, it will cause business data inconsistency.

The correct way to use shared block storage is to use cluster file system for unified management of block devices, such as GFS, GPFS and so on. ASM is recommended for unified management of storage volumes and file systems in typical Oracle RAC business scenarios.

Can I mount shared block storage across regions?

I can't. You can only mount shared block storage to ECS instances in the same region and availability zone.

How many blocks of shared block storage can be mounted on an instance?

When used as a data disk, shared block storage shares the data disk quota with the cloud disk, that is, a maximum of 16 data disks can be mounted on an instance.

Product specification

Two kinds of shared block storage products are currently supported, as shown in the following table.

Product characteristics

Shared access attribute: up to 8 instances can be mounted at the same time.

High performance: up to 30000 random read and write IOPS, 50% higher sequential throughput of 512 MBps than SSD cloud disk and 100% higher than SSD cloud disk.

Large capacity: 32 TiB for a single disk and 128 TiB for a single instance.

Safe and reliable: 99.99999999% data reliability, support to set automatic snapshot policy.

Sales mode and public test scope

Postpaid by quantity and prepaid are supported after commercialization, and only postpaid by quantity is supported during the product public trial.

The price of shared block storage during public testing is subject to a free public testing strategy.

Shared block storage products are available throughout the region during public testing.

Public test purchase entrance

After applying for the public test qualification, click Buy now on the Block Storage Product page, and then select the region and availability zone to purchase shared block storage devices.

Shared block storage performance test command

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