AMI storage configuration

To determine the available storage for Docker

• You can use the LVM commands, vgs and lvs, or the docker info command to view available storage for Docker.

  Note

  The LVM command output displays storage values in GiB (2^30 bytes), and docker info displays storage values in GB (10^9 bytes).

  1. You can view the available storage in the volume group with the vgs command. This command shows the total size of the volume group and the available space in the volume group that can be used to grow the logical volume. The example below shows a 22-GiB volume with 204 MiB of free space.

     [ec2-user ~]$ sudo vgs

     Output:

       VG     #PV #LV #SN Attr   VSize  VFree
       docker   1   1   0 wz--n- 22.00g 204.00m

  2. You can view the available space in the logical volume with the lvs command. The example below shows a logical volume that is 21.75 GiB in size, and it is 7.63% full. This logical volume can grow until there is no more free space in the volume group.

     [ec2-user@ ~]$ sudo lvs

     Output:

       LV          VG     Attr       LSize   Pool Origin Data%  Meta%  Move Log Cpy%Sync Convert
       docker-pool docker twi-aot--- 21.75g             7.63   4.96

  3. The docker info command also provides information about how much data space it is using, and how much data space is available. However, its available space value is based on the logical volume size that it is using.

     Note

     Because docker info displays storage values as GB (10^9 bytes), instead of GiB (2^30 bytes), the values displayed here look larger for the same amount of storage displayed with lvs. However, the values are equal (23.35 GB = 21.75 GiB).

     [ec2-user ~]$ docker info | grep "Data Space"

     Output:

      Data Space Used: 1.782 GB
      Data Space Total: 23.35 GB
      Data Space Available: 21.57 GB

To extend the Docker logical volume

The easiest way to add storage to your Amazon EC2 instances is to terminate the existing instances and launch new ones with larger data storage volumes. However, if you are unable to do this, you can add storage to the volume group that Docker uses and extend its logical volume by following these steps.

1. Create a new Amazon EBS volume in the same Availability Zone as your Amazon EC2 instance. For more information, see Creating an Amazon EBS Volume in the Amazon EC2 User Guide for Linux Instances.

2. Attach the volume to your Amazon EC2 instance. The default location for the Docker data volume is /dev/xvdcz. For consistency, attach additional volumes in reverse alphabetical order from that device name (for example, /dev/xvdcy). For more information, see Attaching an Amazon EBS Volume to an Instance in the Amazon EC2 User Guide for Linux Instances.

3. Connect to your Amazon EC2 instance using SSH..

4. Check the size of your docker-pool logical volume. The example below shows a logical volume of 409.19 GiB.

   [ec2-user ~]$ sudo lvs

   Output:

     LV          VG     Attr       LSize   Pool Origin Data%  Meta%  Move Log Cpy%Sync Convert
     docker-pool docker twi-aot--- 409.19g             0.16   0.08

5. Check the current available space in your volume group. The example below shows 612.75 GiB in the VFree column.

   [ec2-user ~]$ sudo vgs

   Output:

     VG     #PV #LV #SN Attr   VSize    VFree
     docker   1   1   0 wz--n- 1024.00g 612.75g

6. Add the new volume to the docker volume group, substituting the device name to which you attached the new volume. In this example, a 1-TiB volume was previously added and attached to /dev/xvdcy.

   [ec2-user ~]$ sudo vgextend docker /dev/xvdcy
     Physical volume "/dev/sdcy" successfully created
     Volume group "docker" successfully extended

7. Verify that your volume group size has increased with the vgs command. The VFree column should show the increased storage size. The example below now has 1.6 TiB in the VFree column, which is 1 TiB larger than it was previously. Your VFree column should be the sum of the original VFree value and the size of the volume you attached.

   [ec2-user ~]$ sudo vgs

   Output:

     VG     #PV #LV #SN Attr   VSize VFree
     docker   2   1   0 wz--n- 2.00t 1.60t

8. Extend the docker-pool logical volume with the size of the volume you added earlier. The command below adds 1024 GiB to the logical volume, which is entered as 1024G.

   [ec2-user ~]$ sudo lvextend -L+1024G /dev/docker/docker-pool

   Output:

     Size of logical volume docker/docker-pool_tdata changed from 409.19 GiB (104752 extents) to 1.40 TiB (366896 extents).
     Logical volume docker-pool successfully resized

9. Verify that your logical volume has increased in size.

   [ec2-user ~]$ sudo lvs

   Output:

     LV          VG     Attr       LSize Pool Origin Data%  Meta%  Move Log Cpy%Sync Convert
     docker-pool docker twi-aot--- 1.40t             0.04   0.12

10. (Optional) Verify that docker info also recognizes the added storage space.

    Note

    Because docker info displays storage values as GB (10^9 bytes), instead of GiB (2^30 bytes), the values displayed here look larger for the same amount of storage displayed with lvs. However, the values are equal (1.539 TB =1.40 TiB).

    [ec2-user ~]$ docker info | grep "Data Space"

    Output:

     Data Space Used: 109.6 MB
     Data Space Total: 1.539 TB
     Data Space Available: 1.539 TB