Tino Schwarze wrote at about 11:44:29 +0200 on Thursday, June 4, 2009:
> Hi Flavio,
>
> On Thu, Jun 04, 2009 at 08:23:36AM +0200, Boniforti Flavio wrote:
>
> > > Q: Does anyone know?
> > > A: Yes
> >
> > Maybe I'm the only human which thinks a bit more "elastically", but if
> > anybody asks:
> >
> > "Anybody knows why there's difference between the above 2 values?"
> >
> > I'm prone to explain *why* there's a difference and not wasting my time
> > and the time of others for typing simply "yes".
> > But that may be a weird and complex way-of-thinking that is affecting
> > only me :-/
>
> Nope, I tend to think like that as well. :-|
>
> > > Asked and answered. What you were really looking for was:
> > >
> > > Q: Please explain to me the difference between the two number?
> > > A: The file structure under backuppc has little resemblance
> > > to the file structure of the original system. For each
> > > directory, there is essentially a file with the directory
> > > information as it appears on the original system (to handle
> > > permissions and such). This will cause the numbers to differ
> > > across multiple directories. There may be more reasons, but
> > > the question seems so arbitrary and pointless I dont care to
> > > put a lot of effort into getting a definitive answer. Maybe
> > > if you have a good reason why you care why the numbers are
> > > different I might be more interested.
> >
> > The reason which *for me* is worth knowing to which value I have to
> > trust and *why*, is the fact that I have to account for HDD space usage.
> > I'd really be happy using the values that BackupPC shows in the "Host
> > Summary", but if they ain't really what HDD space usage should be, I
> > just want to know which value to consider. If anybody has already done
> > this sort of considerations (HDD space accounting per single host, which
> > corresponds to a single customer), please explain to me his or her
> > considerations.
>
> The short answer is: You cannot account for single host disk usage
> because of pooling.
>
> Suppose, you've got three hosts, all with the same operating system. All
> common files will be in the pool only once. And they will get hardlinked
> every time you do a full backup.
>
> So you get three hosts, with, say, 5 backups each. The /boot/vmlinuz
> file will be shared by all those 15 backups. How would you account disk
> space?
>
> And it get's more complicated in practice. Customer 1 installes Firefox,
> Customer 2 and 3 use Opera. So, now only 2 and 3 share the common
> Opera files in the pool (which might be compressed after all).
>
> Even if you developed some formula how to account for disk space, it
> is very expensive to figure out who shares a common pool file - you'd
> need to scan all pc/ directories and remember inode numbers etc.
>
> My advice: Just account on total amount of data backed up. And this is
> the number you get in the host summary page as "Full Size(GB)" and in
> host status page in the "File Size/Count Reuse Summary" table in
> "Totals" column - here you can also see the pooling effects nicely.
Also, as a rough shortcut, almost all of the storage should be in the
pool/cpool directories, so you can get a good estimate by doing
something like du -s on those directories. Almost all the files in the
pc hierarchy are either hard links to the pool or zero-size except for
the log & admin files in the top directory of each host and the attrib
files in each subdirectory.
------------------------------------------------------------------------------
OpenSolaris 2009.06 is a cutting edge operating system for enterprises
looking to deploy the next generation of Solaris that includes the latest
innovations from Sun and the OpenSource community. Download a copy and
enjoy capabilities such as Networking, Storage and Virtualization.
Go to: http://p.sf.net/sfu/opensolaris-get
_______________________________________________
BackupPC-users mailing list
BackupPC-users AT lists.sourceforge DOT net
List: https://lists.sourceforge.net/lists/listinfo/backuppc-users
Wiki: http://backuppc.wiki.sourceforge.net
Project: http://backuppc.sourceforge.net/
|
