Local disks

Limits

• Local disks are physically located on a single physical server. This increases the risks of single points of failure (SPOFs). The durability of data stored on local disks is determined by the reliability of the associated physical server.
  Warning For example, data stored on local disks may be lost when a hardware failure occurs. We recommend that you make sure to store only temporary data on local disks.

  • To ensure data availability, we recommend that you implement data redundancy at the application layer. You can use deployment sets to distribute ECS instances across multiple physical servers for high availability and disaster recovery. For more information, see Create a deployment set.
  • If your applications do not utilize an architecture that prioritizes data reliability, we recommend that you use cloud disks or a backup service with ECS instances to improve data reliability. For more information, see Disks or What is Hybrid Backup Recovery?.
• After you purchase an ECS instance that has local disks attached, you must log on to the instance to partition and format the local disks. For more information, see Partition and format a data disk on a Linux instance or Partition and format a data disk on a Windows instance.
• Local disks do not support the following operations:
  • Create a separate local disk.
  • Use a snapshot to create a local disk.
  • Attach a local disk.
  • Detach and release a local disk.
  • Resize a local disk.
  • Re-initialize a local disk.
  • Create a snapshot for a local disk.
  • Use a snapshot to roll back a local disk.

Disk categories

Local disks are suited for business scenarios that require high storage I/O performance, mass storage, and high cost efficiency. Alibaba Cloud provides two categories of local disks. The following table describes the categories.

Local NVMe SSDs

• The following table describes the performance metrics of the local NVMe SSDs that the i3 instance family uses.

  Performance metric	ecs.i3.xlarge	ecs.i3.2xlarge	ecs.i3.4xlarge	ecs.i3.8xlarge	ecs.i3.13xlarge	ecs.i3.26xlarge
  Maximum read IOPS	250,000	500,000	1,000,000	2,000,000	3,000,000	6,000,000
  Maximum read throughput (GB/s)	1.5	3	6	12	18	36
  Maximum write throughput (GB/s)	1	2	4	8	12	24

  Note The performance data in the preceding table represents the highest performance levels of local storage in the i3 instance family. We recommend that you use images that contain Linux kernel 4.10 or later, such as Alibaba Cloud Linux 2 and CentOS 8.x images, to obtain optimal performance.
• The following table describes the performance metrics of the local NVMe SSDs that the i3g instance family uses.

  Performance metric	ecs.i3g.2xlarge	ecs.i3g.4xlarge	ecs.i3g.8xlarge	ecs.i3g.13xlarge	ecs.i3g.26xlarge
  Maximum read IOPS	250,000	500,000	1,000,000	1,500,000	3,000,000
  Maximum read throughput (GB/s)	1.5	3	6	9	18
  Maximum write throughput (GB/s)	1	2	4	6	12

  Note The performance data in the preceding table represents the highest performance levels of local storage in the i3g instance family. We recommend that you use images that contain Linux kernel 4.10 or later, such as Alibaba Cloud Linux 2 and CentOS 8.x images, to obtain optimal performance.
• The following table describes the performance metrics of the local NVMe SSDs that the i2 and i2g instance families use.

  Performance metric	Single disk performance		Overall instance performance①
  	ecs.i2.xlarge and ecs.i2g.2xlarge	Other i2 and i2g instance types
  Maximum capacity (GiB)	894	1,788	8 × 1,788
  Maximum read IOPS	150,000	300,000	1,500,000
  Maximum read throughput (GB/s)	1	2	16
  Maximum write throughput (GB/s)	0.5	1	8
  Access latency	Within microseconds

  ^① Overall instance performance data in the preceding table applies only to the ecs.i2.16xlarge instance type and represents the highest performance levels of local storage in the i2 instance family.

• The following table describes the performance metrics of the local NVMe SSDs that the i2ne and i2gne instance families use.

  Performance metric	ecs.i2ne.xlarge and ecs.i2gne.2xlarge	ecs.i2ne.2xlarge and ecs.i2gne.4xlarge	ecs.i2ne.4xlarge and ecs.i2gne.8xlarge	ecs.i2ne.8xlarge and ecs.i2gne.16xlarge	ecs.i2ne.16xlarge
  Maximum capacity (GiB)	894	1,788	2 × 1,788	4 × 1,788	8 × 1,788
  Maximum read IOPS	250,000	500,000	1,000,000	2,000,000	4,000,000
  Maximum read throughput (GB/s)	1.5	3	6	12	24
  Maximum write throughput (GB/s)	1	2	4	8	16
  Access latency	Within microseconds

  Note To obtain the maximum throughput performance of disks for Linux instances, we recommend that you use the latest versions of Alibaba Cloud Linux 2 images. Otherwise, Linux instances may be unable to deliver their maximum IOPS.
• The following table describes the performance metrics of the local NVMe SSDs that the i1 instance family uses.

  Performance metric	Single disk performance	Overall instance performance②
  Maximum capacity (GiB)	1,456	2,912
  Maximum IOPS	240,000	480,000
  Write IOPS①	min{165 × Capacity, 240,000}	2 × min{165 × Capacity, 240,000}
  Read IOPS①
  Maximum read throughput (GB/s)	2	4
  Read throughput (MB/s)①	min{1.4 × Capacity, 2,000}	2 × min{1.4 × Capacity, 2,000}
  Maximum write throughput (GB/s)	1.2	2.4
  Write throughput (MB/s)①	min{0.85 × Capacity, 1,200}	2 × min{0.85 × Capacity, 1,200}
  Access latency	Within microseconds

  ^① Items in the formulas used to calculate the performance specifications of a single local NVMe SSD:

  • In the formula used to calculate the write IOPS, each GiB of capacity produces a write IOPS of 165 for a maximum of 240,000 IOPS.
  • In the formula used to calculate the write throughput, each GiB of capacity produces a write throughput of 0.85 MB/s for a maximum of 1,200 MB/s.

  ^② Overall instance performance data in the preceding table applies only to the ecs.i1.14xlarge instance type and represents the highest performance levels for local storage in the i1 instance family.

Local SATA HDDs

The following table describes the performance metrics of local SATA HDDs.

Billing methods

Local disks are billed along with the instances to which they are attached. For more information, see Subscription and Pay-as-you-go.

Disk initialization sequence

Lifecycle

A local disk shares the same lifecycle as the instance to which it is attached. For more information, see Instance lifecycle.

Impacts of instance operations on data stored on local disks

The following table describes the impacts of instance operations on the data stored on local disks.

References

For information about retired local SSDs, see Ephemeral SSDs.

For information about how to handle system events on ECS instances that are equipped with local disks, see Overview of system events on ECS instances equipped with local disks.