Disk erasure pertains to the erasing of data on each of a node's disks when the node has been released (see Release action) back into the pool of available nodes. The user can choose from among three erasure types before confirming the Release action. A default erasure configuration can also be set.
The three types of erasure types are:
- Standard erase
- Secure erase
- Quick erase
Each of these are explained below.
Overwrites all data with zeros.
Although effectively equivalent to Standard erase, Secure erase is much faster because the disk's firmware performs the operation. Because of this, however, some disks may not be able to perform this erasure type (SCSI, SAS, and FC disks in particular).
Same as Standard erase but only targets the first 1 MB and the last 1 MB of each disk. This removes the partition tables and/or superblock from the disk, making data recovery difficult but not impossible.
A default erasure configuration can be set on the 'Settings' page. Scroll down to the 'Storage' section:
If option 'Erase nodes' disks prior to releasing' is chosen then users will be compelled to use disk erasure. That option will be pre-filled in the node's view and the user will be unable to remove the option.
With the above defaults, the node's view will look like this when the Release action is chosen:
Where 'secure erase' and 'quick erase' can then be configured by the user.
If all three options are checked when the node is released the following order of preference is applied:
- Use 'secure erase' if the disk supports it
- If it does not then use 'quick erase'