Is there any difference between /dev/sd[f-p] to /dev/xvd[a-z] when assigned a device name to a volume in EC2

Question

When assigning a volume to EC2 there are options for setting the device name /dev/sd[f-p] to /dev/xvd[a-z]. does sd series have any different between xvd series? the volume I am attaching is General Purpose SSD (gp2)

Answer 1

• /dev/sd* (SCSI Disk) are set for Boot devices
• /dev/xvd* (XEN Virtual Device) are set for Extension devices

Based on the AWS Docs, the following apply:

1. "/dev/sda1" is reserved for ROOT Volume on both Windows and Linux.
2. "xvd*" is recommended for EBS and Instance Store in Windows.
3. "/dev/sd*" is recommended for EBS and Instance Store in Linux.

Detailed information in the links below:

• Device naming on Linux instances - Available device names - https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/device_naming.html#available-ec2-device-names
• Device naming on Windows instances - Available device names - https://docs.aws.amazon.com/AWSEC2/latest/WindowsGuide/device_naming.html#available-ec2-device-names

Answer 2

This sadly changes based on the generation of instance you are using. For Gen3 (m3, r3, c3, and so on) there is a 1:1 relationship between what you assign as sd[x] to what shows up as xvd[x]. Most of the Gen4 stuff performs this way as well. However, once you get into the instances running Nitro (c5, m5, r5, confusingly i3, others) you don't get vxd[x] devices at all, you get nvme[x] devices instead. The ability of your OS to reliably map your device assignments to actual devices on the box depends on your Linux udev rules.