Hi,
Steffen Dettmer:
> - but the last-resort-emergency deletion may fail because "rm"
> fails with I/O error on aufs
> - we are looking for a way to ensure that deleting from full file
> systems work
As the last-resort-emergency deletion, you can remove the file bypassing
aufs. eg. "rm /rw/fileA", instead of "rm /fileA".
But you should pay attention several things.
- if a process is still opening fileA, then the disk space for fileA is
not freed until the process closes fileA. (especially tmpfile)
- bypassing aufs will make aufs confused since aufs have some info
cached about fileA. But you can discard the obsolete cache by
"mount -o remount /".
> Just in case this idea is not ridiculous:
> some file systems, like ext4, reserve some memory to be available
> to root only. Could aufs reserve some memory to be available to
> XINO files only? This could create a safety margin. Of course the
:::
I don't think it ridiculous.
But aufs doesn't have the backend block devices. It just refers to
another mounted fs (or a dir). It is the "branch" fs which holds the
block device. So aufs cannot reserve some space on it.
In other words, if tmpfs has some reserved space, then aufs will follow
it simply.
> Filesystem Size Used Avail Use% Mounted on
> aufs 505M 456K 505M 1% /
> /dev/sda1 935M 532M 356M 60% /ro
> aufs-tmpfs 505M 456K 505M 1% /rw
>
> You guessed right, /dev/sda1 is the flash media :)
> There are some other tmpfs (e.g. /tmp/).
>
> Normally, the >300 MB free are much more than ever used, but from
> time to time bugs happen.
When the problem happened, how are these free spaces? The several large
files ate all 505MB? And the number of free inodes (df -i) had enough
room?
> Given this environment, would it be recommended to put XINO files
> to an own tmpfs? Are there other recommendations?
If the cause is really several large files, then such separation will
not solve the problem. I'd suggest you to try "direct deletion"
eg. bypassing aufs, described above.
J. R. Okajima
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