Migrate between server flavors

Within the Rackspace Cloud, you have different server flavors from which to choose. You can view the list here.

If you outgrow your server and need more resources, the best option is to scale horizontally by cloning your servers and placing them behind a load balancer. Horizontal scaling, in most cases, works better than vertical scaling. With vertical scaling, you have to take your server offline while you resize up to a larger one. Horizontal scaling allows your existing pool of servers to remain online, serving traffic, while you create additional clones to offload some of the traffic. However, horizontal scaling might not apply in your case, or you might prefer not to use it.

Standard or General Purpose servers default to using local disks rather than block storage volumes as their boot disk. So, it might be unclear how to move to a flavor that boots from a volume such as Compute or Memory.

Limitations

Cloud images created from large servers don’t allow you to take an image and create a bootable Block Storage volume. If you took the image from a cloud server with a root disk, or if the image has a min_disk parameter larger than 127 GB, you can’t create a volume from that image. If you have a 4GB Standard, an 8GB General Purpose server, or anything larger, you fall into this category.

The problem is that the component used to attach images to cloud servers, qemu-img, can’t handle files 127 GB or larger. If you try to attach a too-large image through the API, you get an HTTP 412 invalid image error.

Moving to another flavor

If your Standard or General Purpose server is small enough, you should be able to take an image of your server and create a bootable volume that you can use to boot Compute or Memory flavor servers. To learn more, see Boot a server from a Cloud Block Storage volume.

However, if your server falls under the category listed in the preceding Limitations section, you need to perform a manual cloud-to-cloud migration of the server’s data to move to the other flavor. To learn more, see Cloud-to-cloud migration.