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Ephemeral (Not available in the infomaniak Openstack Public Cloud)

Note

With the introduction of volumes, ephemeral disks are mostly obsolete.

Ephemeral disks can be useful where you want to partition the second disk or have a specific disk configuration which is not possible within the system disk configuration. A good usecase is deep learning VMs with GPU requiring good IOPS and disk performances Ephemeral storage is defined by the virtual machine flavor when the VM is created.

$ openstack flavor list
+----+--------------+-----------+------+-----------+------+-------+-------------+-----------+-------------+
| ID | Name         | Memory_MB | Disk | Ephemeral | Swap | VCPUs | RXTX_Factor | Is_Public | extra_specs |
+----+--------------+-----------+------+-----------+------+-------+-------------+-----------+-------------+
| 1  | m2.small     | 1875      | 10   | 0         |      | 1     | 1.0         | True      | {}          |
| 11 | sp1.medium   | 8192      | 20   | 40        |      | 4     | 1.0         | True      | {}          |
In this case, the sp1.medium flavor has an ephemeral disk of 40GB.

When an instance with ephemeral storage is created, a second disk is defined and mounted automatically on /dev/sdb (by default).

Filesystem           1K-blocks      Used Available Use% Mounted on
/dev/mapper/VolGroup00-LogVol00
                       8547036   1691360   6421500  21% /
tmpfs                  4095860         0   4095860   0% /dev/shm
/dev/sda1               198337     28571    159526  16% /boot
/dev/sdb              41284928    180236  39007540   1% /mnt
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