Hello Steffen, Steffen Dettmer: > On an embedded device, we are using aufs overlaying a tmpfs and a file > system on a disk. When the overlay gets full, it sometimes (but not > always) happens that deleting files does not free space. Is this > normal known (expected) behavior?
Yes, it is normal. When the actual file is on the lower readonly branch, aufs creates a whiteout on the upper writable branch when you remove the file. This logical removing consumes the disk a little and if the upper branch is really really full, aufs fails removing. > What can we do to avoid this? The basic and simple solution is to enlarge the size of the upper branch. But sometimes it may be effective to work around the XINO files. For the details of the XINO files, please refer to aufs manual. - if you have a space on HDD, specify "xino=/path/to/hdd/file" mount option, and aufs creates the XINO file as the specified path instead of the default path (/rw/.aufs.xino in your case). you can use "xino=" option at the remount-time too. - if you specify "trunc_xino" option, aufs tries truncating the XINO files. sometimes it is really effective. - The inode numbering in tmpfs takes the "grow-only" approach. While most of other filesystems try re-using the inode number if possible, tmpfs doesn't. It means when your branch is tmpfs, the size of the XINO files will grow (rather) rapidly. If you can switch tmpfs to other fs, for example ext2 on brd (block ram device) or on HDD, the XINO files will grow mildly I suppose. All these workaround are targetted to the XINO files. If your XINO files are not so large, they will not be effective. I'd suggest you to mount debugfs since aufs prints the size and the number of consumed blocks of XINO files. Also, I'd suggest you to disable CONFIG_AUFS_EXPORT since it will create and maintain the XIB file (a kind of XINO files). If AUFS_BR_HFSPLUS and AUFS_BDEV_LOOP are unnecesary for you, they should be disabled to reduce the module size obviously. J. R. Okajima ------------------------------------------------------------------------------ Introducing Performance Central, a new site from SourceForge and AppDynamics. Performance Central is your source for news, insights, analysis and resources for efficient Application Performance Management. Visit us today! http://pubads.g.doubleclick.net/gampad/clk?id=48897511&iu=/4140/ostg.clktrk
