External Backup of WHS Ver 1 Server RRS feed

  • Question

  • Question regarding what I'm viewing on my external HDD when I view my backup of the server itself.

    I see a series of subdirectories with unique dates of each successive backup.  Inside each is the directory structure and files that were present at each of those dates.

    The series of main subdirectories increases in size with time (which makes sense as the server storage data increased with time).

    But what am I looking at?  Is this a series of separate backups, any of the older ones can be easily deleted and simply retain the most recent?  Or are these tied together somehow?

    The reason I ask that question is because the size of each of these dated subdirectories is almost equal to the size of the external HDD itself, so the sum of those subdirectory sizes far exceeds the size of the external HDD.

    Friday, August 30, 2019 5:00 PM

All replies

  • I believe it is cleverly using indexed/linked file directory structures (something very common in Unix but you don't come across it, at least not in this form, in Microsoft).

    In a nutshell (and this is just supposition based on the same observation you made - I run WHS v1 too) I believe each version of each file exists only once on the hard disk, if the file has not changed n the next backup then it simply cross references the previous version rather than creating the file again.  So a file that has existed and not changed since your first backup will exist on the hard disk once but will appear in the directory structures of each back as a reference.

    The next bit is where I get a little shakey - You hope that the file system knows how many references to a file are made (so if you have 3 backups and the same file is in all 3, there is one file and 3 references to it) and so if you delete the folder representing one backup it actually just deletes one reference to the file, as the file still has 2 references still it remains on the disk. If you then delete the other two backups the file system realises that the last reference to the file has been deleted and therefore the file itself can now be deleted, so suddenly you get the disk space back again.  The scary part is that this is how I would like it to work but I do not know it is the case (and am a little scared to play around with my backups to prove the point). So I always use the backup manager in the WHS console to manage the backups and delete any dates I no longer need as I am sure that will have the right logic.

    Hope that helps even though it is really just an educated guess.

    Friday, September 27, 2019 2:25 PM