Tag: Ephemeral

AWS Storage FAQ

by scmgalaxy KAmazon Web ServicesLeave a Comment on AWS Storage FAQ

What data is stored in ephemeral storage of an Amazon EC2 instance?

Anything that is not stored on an ebs volume that is mounted to the instance will be lost. For instance, if you mount your ebs volume at /mystuff, then anything not in /mystuff will be lost. If you don’t mount an ebs volume and save stuff on it, then I believe everything will be lost.

You can create an AMI from your current machine state, which will contain everything in your ephemeral storage. Then, when you launch a new instance based on that AMI it will contain everything as it is now.

Meaning of “Warning: Please note that any data on the ephemeral storage of your instance will be lost when it is stopped”

There is a difference between “stop” and “terminate”. If you “stop” an instance that is backed by EBS then the information on the root volume will still be in the same state when you “start” the machine again.

Basically, root volume (your entire virtual system disk) is ephemeral, but only if you choose to create AMI backed by Amazon EC2 instance store.

If you choose to create AMI backed by EBS then your root volume is backed by EBS and everything you have on your root volume will be saved between reboots.

If you are not sure what type of volume you have, look under EC2->Elastic Block Store->Volumes in your AWS console and if your AMI root volume is listed there then you are safe. Also, if you go to EC2->Instances and then look under column “Root Device” of your instance and if it says “ebs”, then you don’t have to worry about data on your root device.

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What’s the difference between ephemeral and volume boot disks?

by scmgalaxy KAmazon Web ServicesLeave a Comment on What’s the difference between ephemeral and volume boot disks?

Different boot sources

There are several different kinds of sources to boot from in the DreamCompute dashboard, but they all need to create some sort of virtual disk for the virtual machine to boot. The virtual disk can use either ephemeral storage or volume block storage. When launching an instance, you have several Boot Source options:

  • Image: Launches an instance from the image you choose onto either an ephemeral disk or a new volume disk.
  • Instance Snapshot: Launches an instance from the instance snapshot you choose onto either an ephemeral disk or a new volume disk.
  • Volume: Launches an instance from an existing bootable volume.
  • Volume Snapshot: Creates a volume from the volume snapshot you choose and then launches an instance using that new bootable volume.

Ephemeral boot disks

Ephemeral disks are virtual disks that are created for the sole purpose of booting a virtual machine and should be thought of as temporary.

Ephemeral disks are useful if you aren’t worried about needing to duplicate an instance or destroy an instance and save the data. You can still mount a volume on an instance that is booted from an ephemeral disk and put any data that needs to be saved on it, instead of using the volume as the root of your OS.

  • Can be snapshotted: Useful for duplicating instances or having a copy of an instance at a certain point in time. Snapshots of ephemeral boot disks are stored as Images and count against DreamCompute’s Image quota.
  • Do not use up volume quota: If you have more instance quota, you can always boot it from an ephemeral disk even if you don’t have any volume quota left.
  • Are destroyed when the instance is terminated: This means you will loose your data if you want to delete an instance to free up some instance quota.

Volume Boot Disks

Volumes are a more permanent form of storage than ephemeral disks and can be used to boot from as well as a mountable block device.

Volume boot disks are useful if you need an easy way to duplicate instances and back them up with snapshots, or if you need a more reliable storage solution for your instance than an ephemeral disk. If you use them, you should plan ahead so that you have enough quota for all of the instances you want to boot.

  • Can be snapshotted: Useful for duplicating instances or having a copy of an instance at a certain point in time.
  • Does not get destroyed when you delete the instance (Unless you select the “Delete Volume on Instance Delete” option): You can delete the instance and your data will still exist as a volume that you can boot from later.
  • Uses your volume quota: This can be pricey if you have lots of instances, or take lots of snapshots.

Source – https://help.dreamhost.com/hc/en-us/articles/217701757-What-s-the-difference-between-ephemeral-and-volume-boot-disks-

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