Some Pouta virtual machine [flavors] have ephemeral storage in addition to a root disk. This works as additional storage for the duration of the instance. This storage is not saved with the instance. This storage does not get saved when you create a snapshot of an image. It is not copied along with resizes or migrations. It is especially important to note regarding the io.* flavors that the storage is based on RAID0 arrays optimized for performance, providing no redundancy whatsoever.
For a detailed explanation of ephemeral storage (and other storage options), you can see [the storage concepts] section in the OpenStack user guide.
The ephemeral storage is visible as an additional disk to the virtual machine (usually /dev/vdb). You will need to format and mount it first before you can use it:
sudo mkfs.ext4 /dev/vdb sudo mount /dev/vdb /mnt
You will also need to add an entry to the /etc/fstab file on the machine to make sure the disk gets mounted after a reboot:
sudo umount /mnt/ sudo e2label /dev/vdb EPHEMERAL sudo echo "LABEL=EPHEMERAL /mnt ext4 defaults,nofail 0 2 " >> /etc/fstab sudo mount /mnt
Some legacy flavors (tiny, mini, small, medium, large, fullnode) also contained an ephemeral disk, which was preformatted and mounted automatically.