Differential backup suddenly growing to almost full size

[TeraByte Support]

if the data didn't change the data moved and it depends on the amount of data moved. It's not file based, it's where it's located in the partition.

[mythos]

I believe that the defrag issue is a red herring in this discussion. I regularly defrag my SSDs before an incremental backup and it doesn’t materially increase the backup size.

Cheers

That's an interesting observation. And it agrees with the fact that if some regular windows process (like defrag) caused this it would be an issue for everyone. But that brings us back to square one regarding the origin of all this. I take it that you've never had your incremental backup suddenly grow too much in one day?

[OldNavyGuy]

But that brings us back to square one regarding the origin of all this. I take it that you've never had your incremental backup suddenly grow too much in one day?

In your original post (and your thread title), you said it was differential backups.

Now you're saying it's incremental backups?

Two entirely different things.

[mythos]

I've written about 10 different times that it's DIFFERENTIAL. I just made a mistake on the message above.

[Bob Coleman]

I believe that the defrag issue is a red herring in this discussion. I regularly defrag my SSDs before an incremental backup and it doesn’t materially increase the backup size.

Cheers

I don't know if it's defrag or not, but don't overlook what OldNavyGuy said about incremental vs differential. If you are really using an incremental strategy each new backup will probably be relatively small whatever the underlying cause of changes.

A long time ago I asked some questions about differential vs incremental. This is from memory now, but I think it's accurate.

The difference between differential and incremental backups is kind of a fuzzy concept and has more to do with backup strategy than with a fundamental difference between the two.

There are really only two kinds of backup: Full and Changes Only.

Full is fairly obvious: Back up everything.

For Changes Only, one has to specify an existing backup file. The backup file about to be created will consist of only the changes from the existing backup file. If the existing backup file specified is a full backup there is no fundamental difference in the Changes Only backup created whether it will subsequently be used as the the existing backup for an additional Changes Only backup or not.

To repeat, there is nothing that makes a Changes Only backup based on a Full backup inherently different whether or not this Changes Only backup will subsequently be used as the existing backup for another Changes Only backup. If it is, then the subsequently created Changes Only backup will be an incremental backup because it contains differences from a previous Changes Only backup, not differences from a Full backup.

Back to the original poster's issue, I don't know why one of a series Changes Only backups based on the same Full backup is unexpectedly large, but with regard to the statement (paraphrased) "Once it grows it never decreases", yes, as already explained that will be the case if Changes Only backups continue to be made using the same Full backup as the existing backup file which is more or less the definition of differential backups.

Putting aside, for the moment, the question of what caused one Changes Only (differential) backup to be large, if one wants to continue to make Changes Only backups which are not large, these will have to be made specifying the large one as the existing backup file. The new one will then be an incremental backup by definition because it was based on a previous Changes Only backup rather than a Full backup. That's just the way it works.

There are probably good reasons to not have a large group of incremental backups, but there is no way to have a large group differential backups based the same Full backup where any one will get smaller than the previous one. Again, that's just the way it works.

[TeraByte Support]

3 times in less than two months

Seems like something that happens infrequently like some type of occasional maintenance windows does - perhaps that defrag?

[mythos]

It would be helpful if people actually read my posts before going on at length about the differences of incremental and differential backups. I am WELL AWARE of what each one is. My comment about the differential not shrinking back was a CLEAR answer to what user "Terabyte support" asked.

My issue is NOT that the differential grows in size. It's that it grows to almost FULL size in a SINGLE DAY. I've mentioned this several times already. Not sure what else I can do to make it clear.

[OldNavyGuy]

I have run some tests on differentials in the past day, and they work as expected.

I ran the standard Windows Optimize, and a third-party optimizer on the SSD as part of the tests, with minimal differences in file size.

The term "defrag" has been used a few times in the thread, and for those who don't know, "defragging" (literal use) an SSD is strongly discouraged...that's what "optimize" is for...two different things, for two different types of drives.

The system is running Windows 10 22H2 fully patched, using IFW 3.59.

You are not the only one who reads this thread, so making the distinction between differentials and incrementals is relevant (by the way, you can edit your posts to correct mistypes like incremental).

As you mentioned, if this were an IFW issue, it would have been reported by others...so it appears to be unique to your system.

As mentioned previously a few times, you will need to dig deeper into what's happening on your system.

No one here can do that for you.

Monitor file and folder changes (tools posted above), processes that modify the system (Sysinternals' Process Monitor is a great tool for that), scheduled tasks that have run, and what they do (Nirsoft's TaskSchedulerView is highly recommended).

I don't think this is an IFW isssue.

Good luck.

[mythos]

They work as expected until they don't...
This is not something that happens every day so don't expect to find any results in a single day of testing. As I mentioned it has happened 3 times in almost 2 months. So if you'd really like to see if it happens in your system too you'd have to keep taking differentials for a much longer period than a single day.

Also, mentioning things that are irrelevant to the question asked in this thread (like what each type of backup is) just because other people might read it makes no sense, but whatever floats your boat...

[OldNavyGuy]

What floats my boat is people doing some troubleshooting, and posting what they've done to investigate their issue.

I don't see that you've posted anything relevant to troubleshooting steps (yet you seem to know that it's not a scheduled task).

Doesn't sound like someone who is "experienced" (knowing the difference between backup types, what does and does not affect system changes).

Instead of ranting on whether people are reading your posts, or responding in a "relevant" way, you might roll up your sleeves, start digging in, and see what's up with your system.

You've been given some suggestions on tools you can use (free) to get going on that.

Simple first step would be to roll back to an earlier version of IFW and see if the same thing happens...yet I don't see where you've tried that.

Tech Support may be able to assist you in rolling back to a version earlier than 3.56, which is the "legacy" version that's still available for download on the TU site.

Saying it worked in Windows 7, it does...and then it doesn't in Windows 10, is not a relevant data point. They are two entirely different OS's.

Continuing the back and forth without any further information on what your system is doing, or has done between backups, makes no sense.