Why does my EBS volume fail to attach to my EC2 instance when I try to attach my volume for the first time?

Short description

Some Amazon EC2 instance types require the use AWS Scalable Reliable Datagram (SRD) for high Amazon EBS performance. The following are SRD-capable EC2 instance types:

• C6a
• C6in
• C7g
• Inf2
• M6a
• M6in
• M6idn
• M7g
• R5b
• R6a
• R6in
• R6idn
• R7g
• Trn1
• Trn1n
• X2idn
• X2iedn

Resolution

When you attach an existing Amazon EBS volume to an instance type that requires SRD for the first time, Amazon EBS automatically modifies the existing volume. Then, Amazon EBS moves the volume to an SRD-capable infrastructure. You can apply only one modification at a time to a volume. If you try to attach your volume when a modification is happening on the volume, then Amazon EBS can't move the volume to the SRD-capable infrastructure.

When an existing EBS volume fails to attach to the SRD-capable instance, a notification is sent to your AWS Health Dashboard. Review the notification for details about the activity that's delaying the move to SRD-capable infrastructure. The activity might take up to 48 hours to complete. Wait until the original volume modification is completed, and then attach the Amazon EBS volume to the SRD-capable instance again.

If you must access data from your Amazon EBS volume, then attach the volume to an instance type other than what's listed in the notification. After the modification is completed, attach the Amazon EBS volume to your SRD-capable instance.

Example notifications

Note: The following examples use an R5b.8xlarge instance type.

If you initiated the existing modification, then you receive the following notification:

"r5b.8xlarge is an SRD capable instance. In order to give you the benefit of the performance of an r5b.8xlarge instance, we have to move your volume to SRD capable infrastructure with the modifyVolume process. We are unable to perform the modification operation at this time because your volume is already undergoing modification. You can track the progress of the current modification with the describe-volume-modifications API. Once the modification is completed you can attach the volume to the instance r5b.8xlarge. If you urgently need to access data from this volume, please attach it to any instance family other than C6a, C6in, C7g, Inf2, M6a, M6in, M6idn, M7g, R5b, R6a, R6in, R6idn, R7g, Trn1, Trn1n, X2idn, and X2iedn.”

If Amazon EBS initiated the existing modification, then you receive the following notification:

"r5b.8xlarge is an SRD capable instance. In order to give you the benefit of the performance of an r5b.8xlarge instance, we have to move your volume to SRD capable infrastructure with the modifyVolume process. We are unable to perform the modification operation at this time because of an operational activity being performed by EBS on the server hosting your volume. Your volume is in a healthy and fully redundant state. We will send an update as soon as the operational activity is complete. You can then attach the volume to the instance r5b.8xlarge. This operational activity may last for up to 48 hrs. If you urgently need to access data from this volume, please attach it to any instance family other than C6a, C6in, C7g, Inf2, M6a, M6in, M6idn, M7g, R5b, R6a, R6in, R6idn, R7g, Trn1, Trn1n, X2idn, and X2iedn."

Related information

In the search for performance, there's more than one way to build a network

Amazon EC2 instance types