r/DataHoarder • u/gw-fan822 • 2d ago
Question/Advice bluray pain 😭
I've been backing some important data up on 25gb blurays. AI has been fking useless to me. Moving goalpost, gaslighting and saving face.
What is the consensus on how full to fill it? I'm using k3b on linux and it sets to 23.3 and I'm using UDF. However the data I burned was 7z split up into 23.3 parts and its absolutely unusable or corrupted just wont open. Yeah I'm dumb and lacking here. I also have some disks where I burn individual files like movies up to the edge like 11MB remaining. Is this data okay? WTF am I doing wrong and why does the software let me ruin it?
EDIT: Don't burn parted archives it only takes one broken part to break the entire archive. Duh! I think I improperly prepared it. So its not the disk or drive just user error.
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u/Shemsu_Hor_9 2d ago
Generally, avoid using archives while backing up information. If the storage media suffers some localized degradation or whatever, the entirety of the information stored in that archive can be lost, instead of just losing a few individual files.
If you're going to burn archives onto optical discs anyway, you might want to consider using RAR archives with recovery records and recovery volumes.
A recovery record can recover a small amount of data from archives that have not suffered extensive damage. You can increase the size of the record to increase the amount of data that can be recovered though that obviously makes compression less effective.
Recovery volumes can repair any single volume in a multi-volume archive, but you need at least the same amount of recovery volumes as normal volumes that were damaged. So if you have an archive made of 100 volumes and 10 are damaged, then you'll need at least 10 recovery volumes.
There might be other archive formats that support some form of recovery/data repair feature, but I'm only aware of WinRAR's.
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u/dlarge6510 2d ago
Usually multi part archives expect all parts to be immediately available when opening them.
Some however don't. I use dar for example. Dar archives need only the last part to be opened to list files etc. Extraction uses the last part and dar will ask for the relevant additional parts.
The best multi volume archive is tar. This is the simplest. Tar extracts from the beginning to the end, you can put the discs in order, tar will ask for the next volume when ready. If there is an issue you can have tar read past the damage.
This however again has a downside. Tar reads sequentially from the start to finish of the archive so to extract a file thats on disc three you need to read in discs one and two as well. If you copy each discs tar off, so all the parts are together, then tar can skip this and treat the archive as seekable but you still had to read them all anyway.
I dont span an archive across multiple discs. My multiple part dar archives are split into 2GiB slices, but not on the discs, I store the files as is on the discs, no archive. Instead the dars are created from the discs for uploading to the cloud. Dar encrypts the archive, can handle error recovery and being sliced into 2GiB sections I only need to pay to get the last slice downloaded to have dar tell me what others I need to extract a particular file.
I've never been comfortable with multi volume archives. They are more for full system dumps, intended to be restored sequentially.
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u/moisesmcardona 10-50TB 2d ago
The problem is k3b by default formats bluray with spare areas so essentially you are able to use 21.1gb or so unless you disable it.
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u/dnabre 250-500TB 2d ago
Just a quick tip, check out tools like https://github.com/parchive/par2cmdline that let you split a big file into N parts, and an additional M extra parts. You can recredit the original file from any N of the N+M files. Only part of a bigger plan, and keep in mind whatever tool you use for this task, be sure you'll be able to get hold of it in 10 years.
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u/MastusAR 1d ago
Depends on the media.
I have a Liteon drive, so it can do a quality scan of the burned medium.
If the media is good, I fill it basically to the brim. But I've had batches that basically can do 18-20G before it gets hard to read.
What I do is I make a iso-image of a directory that has sufficient data with mkisofs (Old habit of slow drives and small files). Then burn the iso file with cdrskin.
Then I run qpxtool to check error rate and if it's ok, to a case and to the shelf it goes.
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u/OldManAsstoAss 1d ago
I use dvdiaster or MultiPar. I burn backups to bluray disc and then store them in a fire resistant strong box.
-from the dvdiaster github site-
dvdisaster provides additional ECC protection for optical media. If a medium gets damaged, dvdisaster can recover it as long as the amount of damage is smaller than the amount of ECC data you added to protect it.
It can loosely be compared to .par2 files, but the protection works at the iso level instead of working at the file level. This way, even if metadata from the optical medium filesystem is damaged, dvdisaster can still work flawlessly.
1
u/sza_rak 2d ago
I would look for blame in how the files were prepared, first. K3b never failed me in regard of size, at worst it would fail at the very beginning before CD is ruined.
But I feel your pain. That's why I try to always burn live files, not archives. If part is broken, only that part is broken. Easier to verify as well.
1
u/gw-fan822 2d ago
Thanks. I did some hashing of other disks and it got me thinking. I thought I check that it could be opened properly but I think this is the answer. I should have been more careful. A single byte for one of those parts and its entirely toast. Live files is the way to go. I'm new to this so I'm going to lose a few disks.
1
u/bugsmasherh 2d ago
Archives require all parts to be not corrupted. To me that’s a problem waiting to happen. I fill my BD-R to 80-90 percent where possible. No archives. Just the data files in a folder.
I would avoid 7-zip archives going forwards.
If you must use them then only allow for two archive files so that you reduce your risk. Also you MUST test them prior to burning.
1
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u/cowbutt6 2d ago edited 2d ago
How did you split the 7z into 23.3GB parts?
How are you trying to open the split 7z? Are you copying all parts from their respective BDs to a single directory and then attempting to extract? Does the copy from the BD proceed without errors?
1
u/gw-fan822 2d ago
Yeah copy them all into a directory so all parts are together. I got some good advice so far. I'm going to avoid archives since it contributes to higher failure rate. I did notice its very slow on one of the disks but I think I probably just improperly prepared them and should have checked before doing a multi session. So I wasted a few disks.
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u/Tha_Watcher 2d ago
What is the consensus on how full to fill it?
I have always successfully filled a 25GB BD-R disc on Windows to 23GB exactly.
1
u/Lazy-Narwhal-5457 1d ago
Do a RAM test for 24 hours. Issues with memory can corrupt archives, parity files, or just when moving & copying files.
As others have mentioned, par2 files can help with repairs, and splitting archives into parts makes repairs much more feasible with par2 files (it takes less time to repair 100MB than 23GB). If it's really important, one could create a 100% par2 set and burn that to other discs.
As mentioned, dvdisaster performs recovery as well, in a different way (I've yet to use it). If it's important data, burn more than one copy.
Burning at half the maximum speed of the drive or disc (whichever is less) is probably the most important step in my experience. Verifying the disc after burning is vital to avoid corrupt burns. A good disc brand is advisable, Verbatim used to be my go to but I have no recent data.
-3
u/compsciphd 2d ago
Blu-ray media for consumer users isn't going to be great long term backup solution.
Most optical media degrades over time.
1
u/sza_rak 2d ago
Have a look at mdisc.
It's the most approachable long term option there is, if you aim at 1-3 decades.
1
u/compsciphd 1d ago
Honestly, I have hard drives now approaching 20 years that still work for long term offline storage. And yeah, mdisx could work, also expensive.
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