Hyperbackup shrinks used space in volumes

[Mark Squicquero]

I just ran Hyperbackup to a directly attached usb drive. At the start Vol1 was 6.1Tb used, and Vol2 was 3.1Tb used. After it finished successfully. the sizes drastically changed. Vol1 now shows 1.6Tb used and Vol2 shows 2.1 TB used. This is impossible. I've checked and everything seems intact, nothing missing. So how can 6.1TB of data suddenly become 1.6TB of data and not lose anything? Very perplexing. Any insight would be greatly appreciated. Thanks

 

[Rusty]

Can you share what type of backup have you done? Is it the default HB one, or pure rsync? What type of content is it (documents, or media for example)?

Keep in mind that HB supports file-based deduplication so that might also play a role in this as well as settings in the backup task (compression for example depending on the type of data).

 

[Telos]

Keep in mind that HB supports file-based deduplication so that might also play a role

Why would a de-duplicated USB backup affect the source content on the NAS? Something is off-kilter here.

 

[zombiephysicist]

I have long noticed that Hyberbackup somehow compresses the source data way tighter upon backup. This is without engaging compression option.

One thing I was guessing is maybe Hyberbackup packages multiple files into singular globs. This would reduce waste because of block sizes. So if your drive has 4k block sizes, but your file is only 128bytes, you are wasting a lot of space. If you are backing up a LOT of small files, that can add up. But this is just speculation on my part.

My delta is not that extreme however. I have, say 4TB of source data, and the full hyberbackup somehow only takes 3TBs. It's been that way for years and across multiple versions, and multiple 'fresh starts'.

 

[Telos]

I have long noticed that Hyberbackup somehow compresses the source data way tighter upon backup

Seems odd. I would not expect backup software to be finagling with the source files it was backing up. That sounds like a disaster waiting to happen.

The OP stated:

At the start Vol1 was 6.1Tb used ... Vol1 now shows 1.6Tb used

That is concerning if Vol1 was only backed up, and not restored.

 

[zombiephysicist]

Seems odd. I would not expect backup software to be finagling with the source files it was backing up. That sounds like a disaster waiting to happen.

The OP stated:


That is concerning if Vol1 was only backed up, and not restored.

I very much agree with your assessment. But it's always been like this for me. More curiously, I have restored (and verified) from such back ups about 6 or so times, and it has been fine. I just dont get it. It somehow magically uses less space on the backup than the source.

What is worse, I just assumed that "that's just the way it is" but gauging from your surprise, now I'm more concerned about it. Weird.

 

[Mark Squicquero]

Can you share what type of backup have you done? Is it the default HB one, or pure rsync? What type of content is it (documents, or media for example)?

Keep in mind that HB supports file-based deduplication so that might also play a role in this as well as settings in the backup task (compression for example depending on the type of data).

I just used the simplest form of HB, No dedup, no rsync. Just simply backup. The data is really all types: PDF's, music, video, text. some apps. I just don't understand why anything would change on the source (NAS).
Thanks,

 

[Telos]

I don't think we're going to get past speculation here, given the information available to us. I recommend you open a support ticket with Synology.

 

[Mark Squicquero]

I don't think we're going to get past speculation here, given the information available to us. I recommend you open a support ticket with Synology.

Just submitted a ticket. Thanks.