It's important to realize that a mixed V3/V4 installation will use more
inodes than just V3 or V4 alone. If you migrate an existing V3
installation to V4 (using BackupPC_migrateV3toV4), the inode usage to store
the backup trees will double, while the inode usage to store the pool files
will be the same.
While V4 doesn't use hardlinks (except transiently for atomic renames etc),
there are cases where a pure V4 installation will use more inodes than V3.
Here's an explanation. In V4, each directory in a backup tree consumes 2
inodes, one for the directory and the other for the (empty) attrib file.
In V3, each directory in a backup tree consumes 1 inode for the directory,
and everything else is hardlinked, including the attrib file. In both V3
and V4, each pool file consumes one inode.
So when you migrate a V3 backup, the number of inodes to store the backup
trees will double. The pool inode usage shouldn't change much, but with
lots of backups the former number dominates.
In a new V4 installation the inode usage will be somewhat lower, since in
V4 incrementals don't store the entire backup tree (just the directories
that have changes get created). In a series of backups where the directory
contents change every backup, including the pool file, V4 will use 3 inodes
per backup directory (directory, attrib file, pool file), while V3 will use
2 (directory, {attrib, pool} linked). So the inode usage is 1.5 - 2x.
Craig
On Sat, Jul 15, 2017 at 1:51 PM, Bzzzz <[email protected]> wrote:
> On Fri, 14 Jul 2017 15:11:36 +0300
> Tapio Lehtonen <[email protected]> wrote:
>
> > Running BackupPC 3 on Debian Wheezy. Ran out of inodes on 250 GB
> > filesystem, max inodes was 15 million.
>
> Use the force, change to a better FS: XFS (w/ the inode64 switch on)
>
> eg: laptop 500GB HD filled @ 80% with many small pictures and dev files,
> df -i returns:
> Filesystem Inodes IUsed IFree IUse% Mounted on
> /dev/sda2 388630464 1265847 387364617 1% /
>
> XFS is also capable to raise the inodes quantity in one command
> while the partition's mounted.
>
> > Can the nightly cleanup now run
> > and maybe release some idodes from the oldest backups?
>
> Best way to know: test it…
>
> > Since the filesystem is Ext4 I can not increase max inodes. Would it
> > reduce the need of inodes if I reduced the number of backups to keep?
>
> google 'inode' to know exactly what it is.
>
> > My quess is users have lots of e-mails stored and since those tend to
> > be small they eat up the inodes.
>
> This is entirely YOUR fault, 'cos before establishing a backup system,
> an admin has to analyze what the data is made of, with the aim of what
> he's gonna do with it. Counting the number of files and their size to
> process is backup's 1.0.1, while checking if you have enough room &
> inodes on the backup device is 1.0.2.
> Not to mention that some self-researches & readings can help.
>
> Jean-Yves
>
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