rootVolumeType accepts only gp2 or io1

[int128]

Instance group spec rootVolumeType seems to accept only gp2 or io1 type.

kops/pkg/model/awsmodel/autoscalinggroup.go

Lines 71 to 72 in 2f3f054

	default:
	volumeType = DefaultVolumeType

A SSD volume is best for production but sometimes cheaper standard is convenient for experimental use.
Is there any reason to limit the volume type?

I think it is nice to support following volume types as well:

• standard
• st1
• sc1

Thanks.

[huang-jy]

See https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/EBSVolumeTypes.html

st1 and sc1 cannot be used as boot volumes -- this isn't a restriction by kops, but by AWS.

[tsuna]

Shouldn't kops reject st1 / sc1 root volumes instead of accepting it and then failing to spin up EC2 instances?

[huang-jy]

@tsuna possible -- that would however require ongoing maintenance to keeep it in line with AWS

[tsuna]

Maybe we could have a warning? "Warning: st1 EBS volumes are not known to be usable as root volumes, your instance might not start". Since the list is small and rarely changes, an alternative would be to have a set of known good types, known bad types. If a known bad type is used: error. Otherwise if not-a-known-good-type then issue a warning.

[huang-jy]

Sounds like a good idea -- perhaps raise a feature request ticket and see if one of the team can pick it up. :)

[ishantanu]

Folks, I just faced this issue while I was unaware that st1 cannot be used as a boot volume. I believe a warning message would be really nice.

[huang-jy]

@iamShantanu101 Raise a feature request ticket and link it to this one, that way those who visit this issue because they, like yourself, have encountered the problem, can +1 it

[ishantanu]

@huang-jy Yes, opening it now.