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Using a flavor with local storage (instead of the network-based storage) gives some implications that you as user need to be aware of.
Local storage is "ephemeral" - Lasting for only a short time
Compute-nodes with local disks are intended to supply ephemeral data storage with higher performance profiles. The downside is a lot less reliability, which is fine as the data should be "ephemeral", meaning "lasting for only a short time". All data that need to be persistent needs to be stored on separate cinder volumes, or other reliable storage locations. The ephimeral disks are lost if:
- The VM is deleted
- The compute-node experiences a disk-failure.
- The VM is "shelved", meaning that it is temporarily placed in cold storage and can be re-created later.
- The "shelve" stores the VM's root-disk, but not any ephemeral-disks.
Slower creation of VMs
Creating a VM where the root-disk is on local storage means that the image you boot need to be copied to the local disk before the VM can be booted. For large images that might involve tens of gigabytes that needs to be copied over the network, resulting in longer creation-times than wat you might be used with from the network-based compute-nodes.
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