Sections of this module:Introduction
Volume (block) vs Object storage
How many cores do I need?
Can I benefit from several VMs?
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Each instance you start on the cloud comes with a certain amount of On-Instance storage, also called ephemeral storage, which appears as two separate hard disks: The primary and secondary disk. When you launch an instance (which you will do in Module 7), you will choose a “flavor”. The flavor determines the number of CPUs of your VM and also the sizes of the two disks on the On-Instance storage. The primary disk is saved with Snapshots which you take of the instance. The secondary disk is not backed up with Snapshots!
Example: In the flavor “m1.small”, you get a primary disk of 10GB. The secondary disk is 30GB—480GB depending on the flavor you select and your allocation. The first disk (10GB) is backed up when you take a Snapshot, whereas the second, larger disk is not included in the snapshot.
You can use the On-Instance storage as block storage, for example for your programs to read/write files to, or to operate your databases.
On-instance storage is regarded as ephemeral — when you terminate your VM, or an unplanned re-start of the Hypervisor takes place in the NeCTAR Node, the data will be lost and cannot be recovered! You should treat it as scratch space and keep important data in either volumes or the object store.
Not all flavors provide a secondary disk. At the time of writing, the following do:
- Collection of images called “standard-v2”: Starting from flavor m2.large and bigger.
- Collection of images called “standard”: Starting from flavor m1.small and bigger.
For more information on on-instance storage, please refer to the NeCTAR support website