Google Developing "DM-BOW" For Using Drive's Free Space For Data Snapshots

Written by Michael Larabel in Google on 23 October 2018 at 09:15 PM EDT. 15 Comments
Google engineers are developing the DM-BOW device mapper driver with plans to use the code on Android devices to provide a restoration path should a system upgrade fail.

The Device Mapper BOW driver in this context is short for "Backup On Write." With the EXT4 file-system commonly used by Android devices not offering native snapshot abilities for backup/restoration, DM-BOW sits underneath to provide snapshots and restore support.

The DM-BOW driver can track the drive's free space and then use the drive's free space for backing up any data being overwritten. If a problem occurs, the file-system can then be unmounted and through a user-space utility it can restore the data preserved in the drive's free space.

When dealing with data not necessary for backups, the DM-BOW driver has a pass-through mode where the data isn't copied.

A working prototype of this new Linux kernel driver was posted today on the kernel mailing list. At this stage it's under a "request for comments" flag and thus not being called for inclusion into the mainline kernel until the code has matured. It will be interesting to see how quickly Google rolls this out with future Android updates.
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