Storage Service Selection

Service Applicability Principles

You need to select a proper storage type based on service scenarios. The following aspects must be considered:

1. Available access mode: After EVS disks or SFS file systems are attached to a host, they are displayed as file system paths in the OS and can be directly accessed by upper-layer applications. OBS needs to be accessed by service applications using dedicated SDKs or APIs. You need to know the acceptable access modes of services. For database applications that require direct raw disk mapping, only block storage (EVS) can be used.
2. Shared or not: EVS supports sharing. You need to select the sharing feature during purchase and use the dedicated cluster software to manage shared disks. SFS and OBS support sharing. Therefore, you need to analyze whether the content to be stored needs to be shared by multiple nodes based on service scenarios.
3. Storage capacity: Different storage types support different capacities. You need to estimate the required capacity level based on the current service volume and future development to select a proper storage type.

   Table 2 Minimum and maximum capacity of the storage service

   Storage Type		Minimum Capacity	Maximum Capacity
   EVS		10 GB	32 TB
   SFS Turbo	20 MB/s/TiB	3.6 TB	1 PB
   	Others	1.2 TB	1 PB
   SFS general-purpose capacity-oriented		0	Unlimited
   OBS		0	Unlimited

Performance Matching

The performance metrics of storage services include transmission bandwidth, IOPS, and latency, as shown in the following table. You need to select the appropriate storage service and specifications based on the performance requirements and specifications of the service system.

In addition, EVS and OBS have no restrictions on the size of stored objects. SFS general-purpose Capacity-Oriented is not suitable for applications with massive small files smaller than 1 MB. SFS Turbo and subsequent SFS General Performance-Oriented can support massive small file applications.

Cost Optimization

You need to consider costs when selecting a storage type to reduce storage costs while meeting service performance requirements.

1. Select the storage service with the lowest unit price while meeting service performance requirements.
2. For storage (EVS and SFS Turbo) billed by specifications, predict the service increment and monitor the capacity. You are advised to reserve 15% to 20% as the scale-out threshold to prevent resource waste caused by excessive capacity specifications.
3. For pay-per-use storage (general-purpose SFS and OBS), plan the usage and purchase resource packages to reduce costs.
4. You can plan lifecycle management policies for storage (general-purpose SFS and OBS) and move cold data to infrequently accessed storage in a timely manner to reduce costs.
5. For services that require large storage capacity and long data retention period, you can reconstruct the service application layer and combine different types of storage (for example, combine EVS/SFS Turbo and OBS) to optimize costs while ensuring service performance.

Reliability Assurance

EVS, SFS Turbo, general-purpose SFS, and OBS use three-replica storage. Data durability meets service requirements, but reliability varies.

• The three replicas of EVS and SFS Turbo are in the same AZ. If the AZ egress or equipment room is faulty, services will be unavailable.
• General-purpose SFS and OBS support both single-AZ and multi-AZ deployment. (Currently, general-purpose SFS supports only single-AZ deployment. Multi-AZ deployment will be available in the future.) For services that require high continuity, you can select multi-AZ instances.
• EVS supports quick data backup and restoration using images, snapshots, and cloud backup. SFS Turbo supports backup and restoration using cloud backup. General-purpose SFS and OBS are generally used in ultra-large-capacity service scenarios and the backup capability is not planned.