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SURFcursus - Extras

This is part one of the Tutorial SURFcursus - 15 Oct 2015. You should have completed (and understood) SURFcursus - part A and SURFcursus - part B, before trying these extras.

The current HPC Cloud offers two storage types: Ceph and SSD. Data stored on Ceph is replicated, to protect against data loss in case of hardware failure. The best practice is to run your operating system on a small SSD image and store your bulk data on Ceph datablock(s).

Working with Storage

When you create a disk image, you must choose where it is stored, under the heading Datastore. You have the choice between local_images_ssd and ceph. The first appliance you imported, created the OS image on local_images_ssd. In this section you will use the ceph Datastore option, by following these steps:

  • Create a new empty datadisk
  • Add the new datadisk to the template
  • Mount the datadisk in the VM

At this point you should not have any running VMs. Let's create a new disk.

Create a new empty datadisk

  • From the UI menu at the left pane, select the Images page under Virtual Resources.
  • Click on the green [+] button on the top.
  • In the Create image window, fill in the form as:
    • Name: my data. You will use this name later in your Template.
    • Type: DATABLOCK.
    • Datastore: 106: ceph.
    • Check the Persistent checkbox.
    • On the Image location: group, choose radio button Empty datablock.
    • Give it a Size in MB: 2000 (is 2GB).
    • Keep FS Type: raw.
  • Click the green button Create on the form, to submit it.

NOTE:

A new image will show on the Images list, and it will keep in status LOCKED while it is being created. When it is created it will come to status READY. Then you still have to format and mount the disk.

Add the new datadisk to the template

In order to let you VM know about the new datablock, you need to add it to your VM's template:

  • Open your Template (or create a new).
  • Select the Storage tab from the menu bar.
  • Click on the + Add another disk button (that will make a new Disk 1), and then choose the my data image you created as a second image.
  • Finish with the Update button on the top to submit it.

Mount the datadisk in the VM

Let's start using the new disk.

  • Create a new VM from the Template you created in the previous step.
  • Once the VM is in RUNNING state, login and check if your new datablock is there:
sudo fdisk -l
  • You need to format the drive now. To format it with the XFS file system install xfsprogs:
sudo apt-get install xfsprogs
  • Mount the datadisk in the VM:
sudo mkdir /data  
sudo mkfs -t xfs /dev/vdb  
sudo mount /dev/vdb /data
  • Arrange the permissions to allow non-root access to the /data directory:
sudo chown ubuntu:ubuntu -R /data

Food for brain:

Create new files or folders in your in /data directory. Logout and login again. Are your changes still there? Shutdown the VM and start it again. Do you see the files on the datablock? Hint: when you start the VM the datadisk is not automatically mounted.

  • From now on, you can transfer files from your laptop on the newly created disk.

Food for brain:

Try to copy a file from your laptop to /data, e.g. with scp myfile [email protected]:/data. Then login to the VM and inspect the changes.

Note:

Shut down all the VMs when you are done