Features and application scenarios of disks - Alibaba Cloud Developer Forums: Cloud Discussion Forums

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[Share]Features and application scenarios of disks

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More Posted time:Jul 19, 2016 15:20 PM
Disks are classified into ephemeral SSDs and cloud disks, where cloud disks are further divided into SSD cloud disks, efficient cloud disks and general cloud disks. The following gives a description of the features and application scenarios of these types of disks separately.
    Ephemeral SSD
    SSD Cloud Disk
    Efficient Cloud Disk
    General Cloud Disk

Ephemeral SSDs
Product features

Ephemeral SSDs use the ephemeral SSD of the instance’s physical server as storage space. They provide the following features:
    Low latency: Under normal conditions, they provide an access latency in microseconds.
    High random I/O: They provide a maximum performance of 12,000 random IOPS.
    High throughput: They provide a maximum performance of 300 MB/s I/O throughput.
    Limited data reliability: Since the ephemeral SSD uses a single physical server, the data reliability is determined by the reliability of the physical server; there are likely SPOF risks.It is recommended to implement data redundancy at the application layer to ensure data availability.
    Up to 800 GB capacity: A single ephemeral SSD provides a maximum storage space of 800 GB.
    Attaching/detaching not supported: Since the ephemeral SSD uses the local disk of a physical server, it does not support independent attaching/detaching.
    Users cannot upgrade or downgrade the CPU, memory and ephemeral SSDs after ordering.

Application scenarios

An ephemeral SSD features low latency, high random I/O, and high throughput. It is applicable to distributed, I/O-intensive applications with redundancy and scenarios that do not require high data reliability, for example:
    Distributed applications: NoSQL and MPP data warehouse, distributed file systems and other I/O-intensive applications. These applications have their own distributed data redundancy. Ephemeral SSDs can provide low latency, high random I/O, and high throughput I/O performance.
    Logs for large online applications: Large online applications can produce a large amount of log data and require high-performance storage. At the same time, the log data does not require highly reliable storage.
    As a swap partition of an instance: When the memory required by an application exceeds the memory actually allocated, a swap space can be used in Linux. When the swap space is enabled, the Linux system can frequently swap in-use memory pages from the physical memory to the swap space (no matter whether it is a dedicated partition of the existing file system or a swap file). In addition, it can free up space for memory pages that require a high access speed.

SSD cloud disks
Product features

SSD cloud disks use a distributed, triplicate mechanism to provide high-performance storage with stable, high random I/O and high data reliability. They provide the following features:
    High performance: They provide a maximum of 20,000 random read/write IOPS and a maximum throughput of 256 MB/s.
    IOPS: Each GB provides 30 IOPS: Each GB of capacity provides 30 random IOPS and a maximum of 20,000 random read/write IOPS. For example, a 100 GB SSD cloud disk can provide 3,000 IOPS, and a 334 GB SSD cloud disk can provide 10,000 IOPS.
    Note: Expected IOPS performance can be achieved only when the SSD cloud disk is attached to an I/O optimized instance. An SSD cloud disk attached to a non I/O optimized instance cannot achieve the expected IOPS performance.
    Throughput: SSD cloud disk throughput=min{50+0.5xdisk_size, 256 }Mbps; initially 50 Mbps, it increases by 0.5 MBps for each GB, up to 256 MBps.
    Performance baseline:
        When the block size is 4 KB/8 KB, the IOPS can reach up to 20,000;
        When the block size is 16 KB, the IOPS can reach up to approximately 16,300, and the throughput reaches the maximum value of 256 MB/s;
        When the block size is 32 KB, the IOPS can reach up to approximately 8,150, and the throughput reaches the maximum value of 256 MB/s;
        When the block size is 64 KB, the IOPS can reach up to approximately 4,100;
        And so on.
    Data reliability: SSD cloud disks adopt a distributed, triplicate mechanism to provide 99.9999999% data reliability.
    Up to 2048 GB capacity: A single SSD cloud disk provides up to 2048 GB storage space.
    Independent attaching: SSD cloud disks can be attached to any ECS instance in the same zone.

Application scenarios

SSD cloud disks have stable, high random I/O performance and high data reliability. They are applicable to the following scenarios:
    PostgreSQL, MySQL, Oracle, SQL Server, and other medium/large relational database applications.
    Medium/large development and testing environments with high data reliability requirements.

Efficient cloud disks
Product features

Efficient cloud disks adopt the hybrid media of SSD and HDD as the storage media. They provide the following features:
    I/O performance: Provides up to 3,000 random read/write IOPS and a maximum throughput of 80 MBps.
    Data reliability: General cloud disks adopt a distributed, triplicate mechanism to provide 99.9999999% data reliability.
    Performance criteria:
        IOPS: Initially 1,000 IOPS, it increases by 6 IOPS for each GB, up to 3,000 IPOS;
        Throughput: Initially 50 MBps, it increases by 0.1 MBps for each GB, up to 80 MBps;
        For example, a 250 GB efficient cloud disk features 2,500 random read/write IOPS and a throughput of 75 MBps.
    Up to 2,048 GB capacity: A single efficient cloud disk provides up to 2,048 GB storage space.
    Independent attaching: Efficient cloud disks can be attached to any ECS instance in the same zone.

Application scenarios

    MySQL, SQL Server, PostgreSQL, and other small/medium relational database applications.
    Medium/large development and testing environments with high data reliability requirements and intermediate performance requirements.

General cloud disks
Product features

General cloud disks adopt HDDs as the storage medium and use a distributed, triplicate mechanism to provide high data reliability. They provide the following features:
    I/O performance: They provide a random read/write IOPS performance of several hundreds and a maximum throughput of 30-40 MB/s.
    Data reliability: General cloud disks adopt a distributed, triplicate mechanism to provide 99.9999999% data reliability.
    Up to 2,000 GB capacity: A single general cloud disk provides up to 2,000 GB storage space.
    Independent attaching: General cloud disks can be attached to any ECS instance in the same zone.

Application scenarios

    This option is applicable to application scenarios in which data is not frequently accessed or that have low I/O loads. If an application requires higher I/O performance, we recommend using an SSD cloud disk.
    Application environments that require low costs and have random I/O reading/writing.
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