Alternate Storage Types

StratusLab also offers two other storage types to support specific use cases: temporary storage and readonly storage.

Volatile Storage

Many applications have a need for a large storage space for temporary data. StratusLab provides volatile storage for this purpose. The space will be reclaimed (and the data lost) when the virtual machine is terminated.

When starting a virtual machine a volatile disk can be added to the machine using the --volatile-disk option:

$ stratus-run-instance \
    --volatile-disk 10 \

You must provide the size (in GiB) of the disk to be allocated.

As for persistent disks, the volatile disks are not formatted. You will need to find and format the disk in the same way as for a persistent disk.


Start a virtual machine with a volatile disk. Find, format, mount, and store data on the disk. Verify that the data on the disk will survive a machine reboot. (Reboot the virtual machine using reboot within the virtual machine.) Unless you added the disk to the /etc/fstab file, you will need to remount the disk after the reboot. The disk and data will disappear when the machine is terminated with stratus-kill-instance.

Static Disks

Many applications use datasets that are either fixed or change slowly, for example, input databases for a scientific calculation. Since these are fixed datasets, you can take advantage of the virtual machine image caching mechanisms to efficiently cache and duplicate these datasets.

These static (read-only) disks can be attached when starting a virtual machine. As for virtual machine images, these disk images are also registered in the Marketplace. To start a machine with a static disk:

$ stratus-run-instance \
    --readonly-disk GPAUQFkojP5dMQJNdJ4qD_62mCo \

The value used for the --readonly-disk is the Marketplace identifier of the disk. The one used here is a CD-ROM image with a small database of “Flora and Fauna”. You can search the Marketplace for it.

You can find, mount, and use the disk:

$ blkid
/dev/sr0: LABEL="_STRATUSLAB" TYPE="iso9660"
/dev/sda1: UUID="b73f3da6-3ca3-4833-a2ab-8a03d6a47b2c" TYPE="ext4"
/dev/sdb: UUID="2a76d471-02d3-45e1-859f-eef3d2946dbb" TYPE="swap"
/dev/sdc: LABEL="CDROM" TYPE="iso9660"

$ mkdir /mnt/data
$ mount /dev/sdc /mnt/data
mount: block device /dev/sdc is write-protected, mounting read-only

$ ls -lR /mnt/data
total 4
dr-xr-xr-x 1 root root 2048 Jan 26  2013 animals
dr-xr-xr-x 1 root root 2048 Jan 26  2013 plants

total 1
-r-xr-xr-x 1 root root 4 Jan 26  2013 cat.txt
-r-xr-xr-x 1 root root 4 Jan 26  2013 dog.txt

total 1
-r-xr-xr-x 1 root root 5 Jan 26  2013 rose.txt
-r-xr-xr-x 1 root root 6 Jan 26  2013 tulip.txt

Note that the disk is read-only, so you cannot make any changes to this disk.

The disk will appear in the virtual machine exactly as it has been formatted in the reference image. Usually these images are formatted as a CD-ROM (or DVD) image so that they are portable between different operating systems.

When creating such images it is strongly recommended (unlike here) that they be created with a label so that they can easily be mounted by the user without needing to know what device has been assigned.


Run a machine with this disk image. Verify that it is indeed read-only. What happens if you start a second disk with the same image?