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Hierarchy Level


Configure the hard disk to automatically mirror the contents of the CompactFlash card. The hard disk maintains a synchronized mirror copy of the CompactFlash card contents. Data written to the CompactFlash card is simultaneously updated in the mirrored copy of the hard disk. If the CompactFlash card fails to read data, the hard disk automatically retrieves its mirrored copy of the CompactFlash card.


We recommend that you disable flash disk mirroring when you upgrade or downgrade the router.

You cannot issue the request system snapshot command while the mirror-flash-on-disk statement is enabled.


After you have enabled or disabled the mirror-flash-on-disk statement, you must reboot the router for your changes to take effect. To reboot, issue the request system reboot command.


This command has no options.

Required Privilege Level

system—To view this statement in the configuration.

system-control—To add this statement to the configuration.

Release Information

Statement introduced before Junos OS Release 7.4.

Statement deprecated for Junos OS with Upgraded FreeBSD in Junos OS Release 15.1.


To determine which platforms run Junos OS with Upgraded FreeBSD, see the table listing the platforms currently running Junos OS with upgraded FreeBSD in Release Information for Junos OS with Upgraded FreeBSD.