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@lists.sourceforge.net List: https://lists.sourceforge.net/lists/listinfo/backuppc-users Wiki: http://backuppc.wiki.sourceforge.net Project: http://backuppc.sourceforge.net/
