Table of Contents

Ephemeral storage

Some Pouta virtual machine flavors have an ephemeral storage in addition to the 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.

The ephemeral storage is visible as an additional disk to the virtual machine (usually /dev/vdb). You need to format and mount it before you can use it:

sudo mkfs.ext4 /dev/vdb
sudo mkdir /mnt/myephdisk
sudo mount /dev/vdb /mnt/myephdisk

You also need to add an entry in the /etc/fstab file on the machine to make sure the disk gets mounted after a reboot:

sudo umount /mnt/myephdisk/
sudo e2label /dev/vdb EPHEMERAL
sudo echo "LABEL=EPHEMERAL   /mnt/myephdisk   ext4  defaults,nofail 0 2 " >> /etc/fstab
sudo mount /mnt/myephdisk

After the storage has been mounted, you need to change the ownership to be able to read and write data in it. In the following command, we are assuming the username is cloud-user.

sudo chown cloud-user:cloud-user /mnt/myephdisk

Please note that some legacy flavors (tiny, mini, small, medium, large, fullnode) also contained an ephemeral disk which was preformatted and mounted automatically.

Last edited Fri Oct 23 2020