Local disks are located on the physical servers (host machines) that ECS instances are hosted on. They provide temporary block level storage for instances, featuring low latency, high random IOPS, and high I/O throughput. They are designed for business scenarios requiring high storage I/O performance.

Because a local disk is attached to a single physical server, the data reliability depends on the reliability of the physical server, which may cause single points of failure. We recommend that you implement data redundancy at the application layer to guarantee data availability.

Warning
Using a local disk for data storage can carry a risk of data loss in some cases, such as when the host machine is down. Therefore, never store any business data that requires long-term persistence on a local disk. If no data reliability architecture is available for your application, we strongly recommend that you build your ECS with elastic block storage.

Categories

Currently, Alibaba Cloud provides two types of local disks:

  • Local NVMe SSD: This disk is used together with instances of the following type families: i2, i1, gn5, and ga1. The instance type families i1 and i2 apply to the following scenarios:

    • Online games, e-businesses, live videos, media, and other industries that provide online businesses and have low latency and high I/O performance requirements on block level storage for I/O-intensive applications.
    • Business scenarios that have high requirements on the storage I/O performance and availability of the application layer, such as NoSQL non-relational databases, MPP data warehouses, and distributed file systems.
  • Local SATA HDD: This disk is used together with instances of the d1ne and the d1 type families. It is applicable to the Internet, finance, and other allied businesses that require big data computing and storage analysis for massive data storage and offline computing business scenarios. It fully meets the needs of distributed computing business models represented by Hadoop in multiple aspects, such as instance storage performance, capacity, and intranet bandwidth.

Performance of local NVMe SSD

The following table lists the performance of local NVMe SSD of an i1 ECS instance.

Parameters Local NVMe SSD
Maximum capacity

Single disk: 1,456 GiB

Total: 2,912 GiB

Maximum IOPS

Single disk: 240,000

Total: 480,000

Maximum throughput

Read throughput per disk: 2 GBps

Total read throughput: 4 GBps

Write throughput per disk: 1.2 GBps

Total write throughput: 2.4 GBps

Single-disk performance* Write performance:
  • Single disk IOPS: IOPS=min{165 * capacity, 240000}
  • Single disk throughput: Throughput=min{0.85 * capacity, 1200}MBps
Read performance:
  • Single disk IOPS: IOPS=min{165 * capacity, 240000}
  • Single disk throughput: Throughput=min{1.4 * capacity, 2000}MBps
Access latency In microseconds

* Explanation on single disk performance calculation formulas:

  • Write IOPS for a single local NVMe SSD: 165 IOPS for each GiB, up to 240,000 IOPS.
  • Write throughput for a single local NVMe SSD: 0.85 MBps for each GiB, up to 1,200 Mbit/s.

Performance of local SATA HDD

The following table lists the performance of local SATA HDD of a d1ne or d1 ECS instance.

Parameters Local SATA HDD
Maximum capacity

Single disk: 5,500 GiB

Total capacity per instance: 154,000 GiB

Maximum throughput

Single disk: 190 MBps

Total throughput per instance: 5,320 MBps

Access latency In milliseconds

Billing

Local disks charges are covered in the payment for the instances to which they are attached. For more information about instance billing methods, see Subscription and Pay-As-You-Go.

Lifecycle

A local disk has the same lifecycle as the instance that it is attached to:

  • You can create a local disk only when creating an instance that has local storage. The capacity of a local disk is determined by the ECS instance type. You cannot increase or decrease it.
  • When the instance is released, the local disk is released with it.

Operations on an instance affect the data on the local disk

The following table shows how operations on an instance that has local storage affect the state of the data on the local disk.

Operation State of the data on the local disk Description
Restart within the operating system/restart or force restart in the ECS console Retained Both the storage volumes and data on the local disk are retained.
Shut down within the operating system/Stop or force stop in the ECS console Retained Both the storage volumes and data on the local disk are retained.
Release in the ECS console Erased The storage volumes on the local disk are erased and the data on it is not retained.
Downtime migration Erased The storage volumes on the local disk are erased and the data on it is not retained.
Out-of-service (Before the computing resources of an instance is released) Retained Both the storage volumes and data on the local disk are retained.
Out-of-service (After the computing resources of an instance is released) Erased The storage volumes on the local disk are erased and the data on it is not retained.

Related operations

If your ECS instance comes with local disks, you must connect to the instance to format the disk. Unlike cloud disks, you cannot perform the following operations on local disks:

  • Independently creating an empty local disk or creating a local disk from a snapshot.
  • Attaching a local disk in the ECS console.
  • Detaching and releasing a local disk.
  • Increasing the size of a local disk.
  • Re-initializing a local disk.
  • Creating a snapshot for a local disk and using the snapshot to roll back the local disk.