Boot medium

The system is installed on a boot medium, where  the system starts and where internal configuration data are saved . It is possible to install the system on a single disk or on a mirrored boot medium configuration. Mirrored configuration was introduced to improve safety and reliability of the boot medium as it continues to work when one of the disks fails. However, it is still possible to install the system on a single disk and to use it without redundancy. A single disk configuration can be extended to a mirrored boot medium just by adding another disk. It will transform a single disk boot medium to a mirrored configuration which is recommended. However, it is not possible to transform a mirrored configuration to a single disk configuration. The mirrored boot medium uses two disks as active and any other disk as spare disk. Active disks contain the actual system data while spare disks are used to replace active disks in case of an error. The boot medium automatically replaces broken disks with spare disks when at least one is available.

The boot medium panel in GUI is divided into three parts: status, disks and integrity scanner.

Boot medium status:

Status consists of basic information about the boot medium and a tip that displays suggested actions that may improve the boot medium’s  safety. It also informs about  the progress of the rebuild operation (if it is running). The table with the basic boot medium information displays the following fields:

• State:     describes the overall state of the boot medium:   
  • Healthy – this state means that the boot medium is working without issues. However, it is is also present when the system was installed on a single disk. In that case it is recommended  to add another disk to the boot medium in order to     increase redundancy.
  • Degraded – this state means that one active boot medium disk  is not working    and that the boot medium is running on one disk only. This state is possible     only if  there are no healthy spare disks left. It is highly recommended to add another disk to the boot medium.
  • Recovering – this state means that the boot medium is synchronizing one of the spare disks with active boot medium disk. After this process is successfully     finished, the spare disk becomes an active boot medium disk and the boot medium will be in a healthy state.
• Disks: displays the number of active and healthy disks that are present in the boot medium. It also displays the designed number of active disks in the boot medium.     For instance,  as a single disk configuration it displays 1/1 disks and for the mirrored boot medium it displays x/2 where x is the number of currently active and healthy disks.   
• Redundancy:     shows the currently used redundancy of the boot medium. Single means that a single disk configuration is used and mirror means that the boot medium uses a mirrored configuration (two disks).

Disk table:

A disk table displays all disks that form the boot medium. In the first part all active disks are displayed and the second part displays spare disks. By using the “Edit” menu it is possible to display disk details, fail disk or to remove the disk from the boot medium. Failing disk will mark this disk as failed for the boot medium. That disk will be treated by the boot medium  as broken. In case  the active disk is marked as failed and  if any spare is available, it is used to rebuild the boot medium. Manual disk failure may be useful if we have some assumptions that the disk may work incorrectly and fail in the future. It is also possible to completely remove the  disk from the boot medium. After removal that disk is available for use. The removed disk is replaced by a spare disk (if it is available).

Integrity scanner:

Integrity scanner is a tool used for verifying if  the boot medium contains checksum errors. In case any error is discovered during scan, this tool attempts to correct it. In order to manually run the scanner click the  “Run” button. It is possible to schedule boot medium scans. In order to open a scheduler window for the boot medium click on the scheduler button. More information about using scheduler can be found here (link tohttp://wiki.scalelogicinc.com/default/wiki/Scheduler_window)