Managing the ephemeral storage

Depending on the instantiated flavor (m1.tiny, …) a second disk is mounted to the VM under the peripheric /dev/vdb. You may use this space as a normal block device. This space is limited to the VM lifetime and will therefore be destroyed with it.

Choose the amount of ephemeral space

% openstack flavor list
+----+-----------+-----------+------+-----------+------+-------+-------------+-----------+
| ID | Name      | Memory_MB | Disk | Ephemeral | Swap | VCPUs | RXTX_Factor | Is_Public |
+----+-----------+-----------+------+-----------+------+-------+-------------+-----------+
| 1  | m1.tiny   | 512       | 0    | 0         |      | 1     | 1.0         | True      |
| 2  | m1.small  | 2048      | 10   | 20        |      | 1     | 1.0         | True      |
| 3  | m1.medium | 4096      | 10   | 40        |      | 2     | 1.0         | True      |
| 4  | m1.large  | 8192      | 10   | 80        |      | 4     | 1.0         | True      |
| 5  | m1.xlarge | 16384     | 10   | 160       |      | 8     | 1.0         | True      |
+----+-----------+-----------+------+-----------+------+-------+-------------+-----------+

Verify the assigned size

From the VM:

(root) % fdisk -l /dev/vdb
Disk /dev/vdb: 21.5 GB, 21474836480 bytes
[...]

Storage usage

As a partition

% mkfs.xfs /dev/vdb

% mkdir /mnt/ephemeral

% mount /dev/vdb /mnt/ephemeral

With LVM

Create the LVM partition:

% pvcreate /dev/vdb
  Physical volume "/dev/vdb" successfully created

% vgcreate ephemeral /dev/vdb
  Volume group "ephemeral" successfully created

% lvcreate -L5G -n testpart ephemeral
  Logical volume "testpart" created

Format and mount:

% mkfs.xfs /dev/rootvg/ephemeral

% mkdir /mnt/ephemeral

% mount /dev/rootvg/ephemeral /mnt/ephemeral