Retention on Backups - Full deleted, incremental stay?

after using urbackup for a while now I noticed some weird behaviour with the retention.

Lets say I have a client with lots of backups, like this:

  1. inc
  2. inc
  3. full
  4. inc
  5. inc
  6. full
  7. inc
  8. inc
  9. full

Now as time passes by, the oldest one, number 9, will be deleted in the nightly job. But that leaves me with number 7 and 8, two incrementel fullbackups without a corresponding full.
Are those 2 incrementals still functional, so do they still keep the whole content?


UrBackup is designed to be very efficient and to make each backup look like a full backup when it comes to restoring files. The “bits” of the backed-up files are stored separately from the metadata, descriptive information about a file as shown in a directory listing. If one file is stored in two places, even on different machines, UrBackup will keep one copy of the file and use features built into the operating system to give you a view as if each backup had a full copy of the files in their proper locations.

Full backups here mean the Client program tells the Server program about every file on the client computer. Incremental means the Client checks the list it made from the last full backup and only tells the Server about files that have changed. In either case only files that don’t already exist on the server computer are transferred in full. The changes to the metadata are all that’s needed otherwise. Incremental backups tend to run faster so many admins set their systems up to run mostly incrementals and very few fulls.

tl;dr - For file restore purposes there is no difference inside UrBackup between ‘full’ and ‘incremental’ backups. Both contain the full file data as of the time of the backup.

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For file restore purposes there is no difference inside UrBackup between ‘full’ and ‘incremental’
backups. Both contain the full file data as of the time of the backup.

So what are the pros/cons of keeping 10 increments, or 100, or 1000… or 0?

If UrBackUp automatically deletes 50 of my 100 increment backups… nothing is lost?

General Notes
Many users of UrBackup choose to only do Incremental File backups as they are confident that nothing is being missed by the UrBackup Client. In my business I mostly see computers that are not working well, so I tend to be less trusting. I find that daily incremental backups and monthly full backups are sufficient for the offices I manage. Others may want to run quick incrementals several times a day to avoid losing work in progress, such as creative writing or large legal documents that may be harder to redo if lost. Full backups impose an additional burden on the Client and Server to examine and report on each file within the directories marked for backup, whether or not the Client thinks it was changed, so count them as more expensive in computing resources.

UrBackup treats the maximum number of full or incremental backups as an “up to” limit. Given infinite storage, no more than that number will be maintained. Each backup has the overhead of the file structure and accounting info needed to create the appearance of a full backup. More frequent backups and more backup copies being kept will shift a larger percentage of your storage to this overhead instead of keeping actual file changes, which may get dropped as storage fills up and UrBackup deletes older copies to make room.

Interlude: Microsoft Windows doesn’t make things easy.
Linux and UNIX-style operating systems have a reasonably well defined storage hierarchy of things that should be kept forever, things that are expected to be discarded after a process terminates, and things that are in-between, the equivalent of a whiteboard with current project status notes that can be re-created easily but are more convenient to keep close at hand. This lets the administrator assign priorities for backup items and only copy what needs to be retained.

Windows is that messy office with stuff in piles, where every flat surface has stacks of documents from two-year-old lunch receipts to policy manuals to birth certificates and family movies of the kid’s first steps. Backing up the Users directory gets all of that stuff, including the crumpled notes thrown at the overflowing trashcan. Yes, there is a Temp directory you can exclude, several in fact, but each application (looking at you, Google) likes to keep its own cache of precious stuff like pictures from the website you visited by accident six months ago. That all gets dumped into the hidden AppData directory within the Users folder where it’s hard to see. In my offices, every incremental backup I look at is mostly the garbage and extra working copies of files, stuff that changes frequently, with very little new “keep forever” data. As much as possible I try to limit things to the Desktop and Documents folders, and let the monthly Image backup catch the rest.

Choosing a Backup Schedule
Type 1: You’ve got tons of storage in fast RAID pairs, a dedicated local UrBackup Server, a separate offsite UrBackup Server for the critical stuff, and really fast workstations that can do an incremental without the users even noticing. Go ahead and cast a wide net and do frequent backups with large retention counts, just in case Pat wants that draft from four months ago - it’s something to do with apples.

Type 2: You don’t even have enough storage to get a Full Image backup of all the sets for disaster recovery. Set UrBackup for Incremental File backups of only carefully selected folders, and don’t expect to keep things longer than a week. Your Disaster Recovery backup will be on a portable USB hard drive with a free copy of Macrium Reflect that you walk from set to set outside working hours as you have time. If you’re lucky you can get the cost of the drive reimbursed. Professional satisfaction will have to do for the rest.

Type 3: Your UrBackup server is also the main file and database server, and it’s also the only server in the office. You get a single space to install a hard drive, as long as you move a pair of SSDs into an unused floppy bay. You dream of the new 12 Terabyte models but settle for an eBay special of a 4TB drive that says was pretty reliable for them. (This is my world.) You do what you can to restrict backup selections so you avoid most of the daily garbage, and prioritize keeping at least two image backups for disaster recovery because Windows will find something wrong with at least one of them. (You also use Macrium Reflect on critical workstations because only one type of backup is no backup at all.) Let UrBackup manage what’s left over and watch that single backup drive for early signs of trouble.

Hope this helps! --Don

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Kinda hidden in that novella was the answer to your question. Think of each backup as a point-in-time copy of the files at that moment. When UrBackup manages storage by deleting older backups, it will also notice the files that are not needed for later backups (because of changes or deletion since then) and purge the no-longer-needed copies from storage. So yes, things can be lost, but not generally anything currently present on the sets being backed up.

Note also the special case of files that are present on several sets. These will only be deleted after all backups that refer to that version of the file have been deleted. If everyone has the 2021 Policy Manual but April is also keeping the 2019 version she worked on, UrBackup will have to keep both versions in storage, but only one copy of each. The 2020 Manual is no longer saved on any set, so as soon as the last old backup from 2020 is deleted, it will vanish as well.