On Sat, Jul 14, 2018 at 7:41 AM, Jens-Uwe Schluessler <jens-uwe.schluessler at tu-dresden.de> wrote: > Hi, > > why are larger AWS instances c5d.9xlarge and c5d.18xlarge (NVMe SSD > attached) NOT supported by Centos7 AMI, It wouldn't be the first time. I had problems with the i3 instances when they first came out, and I've been dealing with kernel/hardware incompatibilities with Linux kernels since.... 2000. New hardware, and even new virtualization toolkits that interact with both the supporting hardware and the virtualization layer, can have startling interactions. That's why testing is so critical. > while smaller instances (e.g. c5d.4xlarge) are supported? > > Also regular c5.9/18xlarge are supported. See above. Also, the base CentOS 7 3.10.0 kernel is becoming a bit dated: it's 5 years old now. If you have time: can you set up a smaller instance, do kernel updates on top of a CentOs 7 AMI, and see if *that* AMI is compatible with the new instances? Might make for an interesting test and get you a working AMI.