Question files in bad sector of HDD burned in DVD disc - Page 1
Forum section: electronics / general

author: classicsamus87
author_rank: Regular Contributor
timestamp: December 01, 2020, 07:56:53 pm
content: If a rar, zip or exe file is good in a good sector of the HDD and that sector becomes bad (badblock) then these files are corrupted and burned on DVD discs as if they were non-corrupted files? I use ImgBurn, BurnAware Free and Ashampoo Free

author: Nominal Animal
author_rank: Super Contributor
timestamp: December 01, 2020, 08:28:27 pm
content: No. While trying to burn the files, you get read errors, and the burn fails. This is because each sector on the HDD includes error correction bits.You cannot even copy such files without getting read errors.

author: classicsamus87
author_rank: Regular Contributor
timestamp: December 01, 2020, 08:38:08 pm
content: 1) all burning programs fail to burn if the zip, rar and exe file is located complete or a part in bad sector (badblock)? I thought that the burning software just burns and does not read the whole file or corrupted by bad sector of the HDD2) I did a lot of burning of zip, rar and exe files on DVDs only after I realized that my HDD has bad sectors badblocks so I thought they were downloaded to the bad sector of HDD3) does the DVD burning failure per file located in the badblock occur in Windows, firmware or in the burning software?

author: Nominal Animal
author_rank: Super Contributor
timestamp: December 01, 2020, 08:56:41 pm
content: Quote from: classicsamus87 on December 01, 2020, 08:38:08 pmCD/DVD-burning softwarecopiesdata. To copy the data on the HDD, it must be read. If the data has been corrupted, it can no longer be read without errors. Operating systems will not hand off bad data to applications, they fail the read operation at that point.Quote from: classicsamus87 on December 01, 2020, 08:38:08 pmIf the DVDs were burned without errors (I mean, if the DVD-burning application did not complain about read errors), then the files were not in bad sectors.If the HDD marks a sector bad, and you write anything over that sector, the relocation happens, and no data is lost.Quote from: classicsamus87 on December 01, 2020, 08:38:08 pmThe application must read the file to be able to burn it to the DVD. Such read operations either boil down to a system call (like a function, but executed by the kernel itself), or are done via memory-mapping the file. When the file has a bad block, trying to read that part of the file will fail. The system call will return failure instead of success, and accessing the memory map region with the error will cause an exception. (The exact details of that exception vary between OSes, and I'm not 100% sure what it is on Windows. In Linux, Mac OS, and BSDs it is a SIGBUS signal.)Therefore, the burning software will notice it cannot read that part of the file. It is detected by the OS kernel (Windows), and reported to the burning software, when it tries to read that part of the file.(It is possible to write the burning software in a way that ignores all errors, and instead uses either random data, or some previously read data, for that block. It would be both stupid and undesirable for the application to do that, because then users would not know about the errors. All burning applications I have used have complained about read errors if they encountered any. Based on web searches, ImgBurn definitely will show (HDD) read errors. I am not sure about BurnAware Free, because its error code list does not have a code for (HDD) read errors. I could not find any documentation on Ashampoo (just download links), so I do not know whether it reports (HDD) read errors. Note that this is a read error when burning a DVD off of HDD, and not a read error when trying to read a DVD; all three seem to detect the latter, but I only found ImgBurn links talking about read errors with the former.)

author: classicsamus87
author_rank: Regular Contributor
timestamp: December 01, 2020, 09:59:24 pm
content: does reallocation have a limit to exhaust after this limit the badblocks are available and the files are saved and downloaded in them, in this case the zip, rar and exe files are corrupted when being saved in these badblocks? in this case there is also a DVD burning error? preventing the disc from being burned with a corrupted file?you said that the operating system does not deliver bad and corrupted data to burning applications, Windows XP also does this function or is it too old?how many barriers exist that prevent files from being corrupted by badblocks bad sectors if it is recorded in these sectors or good sectors become bad?

author: Nominal Animal
author_rank: Super Contributor
timestamp: December 02, 2020, 08:43:19 am
content: Quote from: classicsamus87 on December 01, 2020, 09:59:24 pmYes. In that case, the write would fail. If you were downloading files, the download would fail, leaving a short file, as if the download was aborted. All current browsers do this. (The reason is that the same code that detectsdisk fullorout of storage spacewill detect write errors too.)In no case will the HDD simply discard the data. The OS will detect a write error, and pass it to the application.Quote from: classicsamus87 on December 01, 2020, 09:59:24 pmIt is not too old. This goes back to 1960s or so, and applies to all operating systems since.If we consider standard C code (standardized since 1989 or so), the code to read data from a file or stream isread_count= fread(buffer,size_each,count,handle);and the code to write data to a file or stream iswrite_count= fwrite(buffer,size_each,count,handle);The two functions are implemented by the standard C library. The library itself implements these calls by one or more syscalls to the OS kernel, which communicates with the peripheral, and transfers the data. All hard disks since at least 1989 can report both read and write errors. Read errors, when the error correction data associated with each sector cannot reconstruct the correct data (this is calledan unrecoverable error); and write errors, when the HDD itself reports a failure. (One possible cause of an error is when the HDD has run out of backup sectors, and cannot avoid a bad sector. However, some filesystems can recover from even that, by fragmenting the file, and internally marking that sector as do-not-use, and simply continues the file data somewhere else.)In any case, whatever error cause the OS reports, the above two standard C library calls will either return a short count (less thancount) or zero.Like I wrote earlier, it is possible for a stupid programmer to NOT CHECK theread_countorwrite_countreturn values, but if they do that, they won't detect running out of disk space and so on. The return value itself does not indicatewhicherror occurred, only that the call could not be (fully) satisfied.Not all errors are from hardware, either. The operating system can for example decide that the file/stream is already as long as the filesystem can support, or the file/stream may not contain any more data. (The standard C library providesfeof(handle)to detect if a previous read could not be fully satisfied because the file or stream ended, andferror(handle)to detect if a previous read or write could not be fully satisfied because some other error occurred.)So, if we consider the browser: Since all browsers tell you the download failed because you ran out of disk space, they will detect a HDD running out of relocatable sectors with a file system that cannot work around that, as a write error. It would take a lot of extra code for a browser programmer to "ignore" that error, but still detect running out of disk space, so we can pretty safely assume that none of the browsers do – especially because the write error is something users do expect to see if it does occur.If we consider the CD/DVD-burning application: It must read the file to be able to burn it to the media. It is possible a stupid programmer deliberately ignores theread_count, but if they do, they won't detectanyerrors reading the file. Because DVD's are often used for backup purposes, detecting that kind of read errors is important – no matter whether one is burning files off a HDD or an USB stick –, as nobody wants to backup garbage: everyone backing up data wants to know their data is intact. All commercial and widely used open source burning software I've used do/did detect those, from the very earliest ones I used on Classic Mac OS back in 1997 or so. After doing a DuckDuckGo web search, I found ImgBurn discussions talking about such read errors, so I know it does have the code to detect such errors; I did not find conclusive evidence one way or another for the two other applications you mentioned.So, if we do a summary:When you download files off a web site, it is possible for errors to creep in due to server-side or browser-side programming errors. The server side ones are suprisingly more common than the browser-side ones, but that has to do with PHP and ASP server-side scripts written by very poor programmers. So, if you download a file that cannot be decompressed, assume the site you downloaded it used a poorly-written scripts, and try to find another host for the file.The TCP/IP connection, and especially secure TLS connections (using https: URIs for the downloaded file), do have checksums/error detection. It is possible for it to fail, and the data to "break" during the network transfer, but it is rare, and with TLS (because of the way ciphers operate), almost nonexistent.It is possible for the browser application to "forget" checking thewrite_count(or equivalent, if using C++, or POSIX C interfaces). It is however very rare.Therefore, we can assume that if a write error occurs – say, because the HDD ran out of relocatable sectors and the filesystem cannot work around it – the browser reports any write errors.Let's assume one or more sectors degrade after that, so that some of the file contents become unreadable.(No HDDs manufactured for consumer use since 1990 or so will deliberately write data to a sector it knows is bad; they will either relocate the sector, using a reserved backup sector, or if none are available, return an error to the OS, which will either work around the error at the filesystem level (marking that sector at the filesystem level as "unusable"), in which case no data is lost; or return a write failure to the userspace application, as a zero or shortwrite_count, or an equivalent depending on programming language and kernel interface used. Like I wrote earlier, even when using memory-mapped files, something very similar happens. One has todeliberatelyignore the error to miss it, and that's very stupid in all cases.)When you try to copy the files, or burn the files to a CD or DVD, the application will tell you that a read error occurred. (Sometimes "I/O Error", for input-output error, as this is usually how the underlying userspace-kernel interface reports theerror cause; noting that standard C does not really expose the error cause here).Again, it is possible for a very stupid burning application todeliberately ignorethe error, but any application that does that is really poor, and will not detect any read errors!(You can sometimes see tutorials showing code without error checking, but usually, more experienced programmers point out how stupid and dangerous omitting theread_countand equivalent checks is.)It is also possible for the CD/DVD burn itself to fail. Each data "sector" – the CD/DVD data is actually a spiral, not concentric rings – contains a lot of error-correction data, so even a few bits per sector being wrong does not mean the sector is unreadable; it is only when there are enough errors the error-correction code cannot correct, that you get a read error. Very, very much like on hard drives!This is also why all good burning software support a verification pass after burning. Essentially, it reads the CD/DVD, and the files it burned, and verifies that the data matches. If it does not match, then the verification will fail. If your burning software has such a verification pass, and you used that pass, you can be pretty sure at that moment, the CD/DVD content matched the data on your HDD, and that data on your HDD was indeed readable (= as stored by your browser or whatever).Finally, the CD/DVD media itself degrades over time. Direct sunlight and UV seems to affect the plastic. (The data is not actually written on the plastic, which is just a transparent disk, but on the thin metal foil on the other side of the plastic.) Scratches make the plastic opaque or distort the laser dot reading the data off the thin metal foil, but can sometimes be corrected by filling or polishing the plastic disk. Remember, the data is on the metal foil on the other side of the plastic, and making the plastic thinner just makes it floppier.)Quote from: classicsamus87 on December 01, 2020, 09:59:24 pmMany; you count them!The HDD itself, and the error correction data (ECC) associated with each sector of data is the first barrier. It detects if the data read no longer can be reconstructed. The error correction codes are quite complex, and it is extremely unlikely that an error goes undetected.On MS-DOS and Windows, you would be using a FAT or NTFS filesystem. Neither of these require that a file must be in continuous sectors. I do not know Windows XP internals if when encountering a hardware write error, it marks the sector unusable, and simply stores that part of the file elsewhere; it certainly is technically possible. I do believe it does. Write errors to storage media used to be a thing many system administrators were aware of and tried to track, I know that much.When the OS kernel detects a failure it did not work around, it will report it to the userspace application. If the application is stupid, it can deliberately ignore and just assume everything always succeeds, but that sort of code is reviled as idiotic. Error checking is, and has been, very important in programming.(Applications that are designed to work okay withshared foldersornetwork driveswill have error checking, because in the Windows environment, file use conflicts in the Windows XP era were very common, and users needed to know if such occurred. And if one checks foranyerrors, it is easiest to just detect and report all of them; anything else requires lots of extra effort, and makes no sense.)Even so, there are no guarantees. A cosmic ray might hit your processor cache right where part of your file being download resides in. This is rare, but even using ECC RAM will not protect you from this. When sliding out the just-burned CD or DVD, the sled itself might scratch the disc, making your burned-and-verified file unreadable. All human-written software has bugs – we just aren't very good at programming! –, so either the browser, the archiver software, or the burning software might change, insert, or delete a byte in one of the files in some specific circumstances, and it might even be one the decompressor does not detect. Nothing is guaranteed, but if you use carefully written software – or at least software that reports errors –, you can bereasonablycertain that your data is retained correctly.Nothing beats backups. Nothing beats physically separate backup storage. I don't mean on different shelves, I mean remote storage in case of fire; on both (detached) HDDs and burned DVDs. Store backup DVDs in a metal box, because metals, even very thin metals, block the plastic-degrading UV best. You can put your offline storage HDDs in the same box, since metals also tend to be conductive, and lessen the possibility of stray strong magnetic fields (say, a Neodymium magnet you or someone else accidentally places nearby the drive) affecting the tiny weak magnetic fields on the platters of the spinny-disk HDD.If you keep concentrating on HDD bad blocks, you are fooling yourself about the possible points of failure. Failure and data loss is ALWAYS a possibility. All you can do, is be sensible about it.

author: classicsamus87
author_rank: Regular Contributor
timestamp: December 02, 2020, 08:20:51 pm
content: Many say that the HDD firmware has the function of reallocating and isolating bad sectors badblocks but I do not know the name the name of this function is ECC?burn dvd use this function?

author: Halcyon
author_rank: Unknown
timestamp: December 06, 2020, 11:49:11 am
content: Why does your profile say you're from New York, your country Andorra and your IP addresses place you in Brazil?Something seems up with this OP.

author: BravoV
author_rank: Super Contributor
timestamp: December 06, 2020, 11:53:09 am
content: Its an experimental chat bot .. we're all just "the experiments" ...Just trace back previous created threads to see what I mean.

author: Nominal Animal
author_rank: Super Contributor
timestamp: December 06, 2020, 05:26:50 pm
content: Quote from: Mechatrommer on December 06, 2020, 12:13:27 pmOh, I answered only because I thought some other newbies might stumble on this topic, and find the information useful.I don't know if classicsamus87 is a bot or someone who just doesn't express themselves well; could be either way, but I don't care nor mind.The topic exists, others might be looking for related information, and giving a simple answer might be useful to some in the long term, so I considered answering worth my time – regardless who or what the asker is.

author: classicsamus87
author_rank: Regular Contributor
timestamp: December 08, 2020, 10:32:50 pm
content: What is the name of the error that DVD burning fails when the zip, rar and exe files are located in some badblock bad sector? this error is Windows, HDD firmware or burning software?

author: AntiProtonBoy
author_rank: Frequent Contributor
timestamp: December 09, 2020, 12:58:26 am
content: Why make duplicate threads of the same topic?https://www.eevblog.com/forum/general-computing/question-hdd-control-badblocks/

author: classicsamus87
author_rank: Regular Contributor
timestamp: December 14, 2020, 07:50:25 pm
content: is there any burning software example ImgBurn that has the option "Ignore reading errors", if I check this option unintentionally and carelessly I will have a burned DVD disc with corrupted files because of the bad sector of the HDD?

author: classicsamus87
author_rank: Regular Contributor
timestamp: December 15, 2020, 12:38:43 pm
content: automatic reallocation of badblock bad sectors (HDD) is present in all drives that have SMART even the HDD IDE drives year 2000? and Windows XP?

author: Jeroen3
author_rank: Super Contributor
timestamp: December 15, 2020, 12:52:32 pm
content: Quote from: AntiProtonBoy on December 09, 2020, 12:58:26 amThe behavior of this user is interesting.

author: ebastler
author_rank: Super Contributor
timestamp: December 15, 2020, 01:20:16 pm
content: @classicsamus87 -- you are getting on everyone's nerves here, and your probability of getting meaningful responses from this forum is rapidly approaching zero. If you want a second chance, may I suggest the following:Don't bullshit us. Give us your real country, for starters, and not some contradictory, made-up data.Don't post the same questions over and over again, and in multiple threads.Give us some context, man! What are you trying to achieve, what problem are you trying to solve? Don't ask apparently random questions about specific details.The "context" bit is (a) a matter of politeness -- we are not here to answer random questions on demand. And (b) it may give you more useful answers. You are working from some assumptions, trying to solve your problem, and these assumptions may well be wrong. But we can't give you better ideas if you do not tell us what your problem actually is.

author: BravoV
author_rank: Super Contributor
timestamp: December 15, 2020, 01:23:51 pm
content: The more you guys respond, the merrier the chat bot AI learn.

author: classicsamus87
author_rank: Regular Contributor
timestamp: December 15, 2020, 02:48:06 pm
content: I'm not fooling anyone, I apologize but I don't have the knowledge you have about HDDs, I'm from Brazil1) I want to understand if the HDD has SMART technology is a total indication that it automatically reallocates and isolates bad sectors (badblocks)2) I am also doubtful whether IDE HDDs from 2000 have SMART technology and automatically relocate and isolate defective sectors and if Windows XP interferes in this process because it is an old system and I used it3) I don't know the year that SMART technology was inserted in HDDs

author: ebastler
author_rank: Super Contributor
timestamp: December 15, 2020, 03:31:37 pm
content: If you are from Brazil, I'd suggest that you set your country flag to Brazil rather than Andorra, and don't enter "ny" as the location in your profile either, which seems to say "New York".In my understanding, bad sector remapping by the disk controller is older than SMART in consumer-grade (IDE/ATA) hard disks. A disk which supports LBA (Logical Block Addressing) should support remapping, I believe, and LBA was introduced in 1994 or earlier:https://en.wikipedia.org/wiki/Logical_block_addressing.SMART, the way I understand it, is just a standard forreportingon the disk health:https://en.wikipedia.org/wiki/S.M.A.R.T.#ATA_S.M.A.R.T._attributes. I would assume that any disk with SMART can also do sector remapping. Doesn't SMART provide the number of remapped sectors as a key indicator for disk health? That implies that remapping takes place, right?You have still not told us why all of this matters to you. What are you trying to achieve? What problem are you trying to solve?

author: classicsamus87
author_rank: Regular Contributor
timestamp: December 15, 2020, 05:32:12 pm
content: thanks for the reply, soon i will change flag but i don't like to provide data as personal as the place where i liveThe oldest HDDs I used are from the year 2000 so I asked if in HDD IDE of the year 2000 from Seagate and WD brands have SMART on wikipedia says 2003the automatic relocation and isolation of defective sectors is linked to SMART so any HDD with SMART has this automatic function?I didn't find a specific name for this relocation and isolation function but I only know SMARTI'm not solving any problems, I just burned DVD discs with important zip, rar and exe files after that I saw that my HDD has bad sectors so I researched about the isolate management in the firmware and I know that it has a limit and I also know a good sector turns into a bad sector

author: Halcyon
author_rank: Unknown
timestamp: December 16, 2020, 09:04:12 am
content: @classicsamus87 -- Prove to me you are an actual human. I am seriously considering suspending your account. It doesn't pass the "pub test"... in other words, something doesn't seem quite right with you.If you care to explain why you want to be part of this community, I will consider your answer as proof of life. ;-)

author: classicsamus87
author_rank: Regular Contributor
timestamp: December 16, 2020, 01:12:39 pm
content: How can I prove that I am human? there is no logic to this question I created a register my informations

author: classicsamus87
author_rank: Regular Contributor
timestamp: December 16, 2020, 08:19:43 pm
content: about the automatic relocation and isolation of defective sectors is managed by the HDD firmware or by Windows? does this automatic function have a name? is present in IDE HDDs from the year 2000?

author: MK14
author_rank: Super Contributor
timestamp: December 17, 2020, 12:31:03 am
content: Quote from: Halcyon on December 16, 2020, 09:04:12 amAlthough, I haven't posted stuff recently here, I've been keeping an eye on things. I got curious, as to this "user" (classicsamus87), and so I investigated the situation.Apparently, they (sadly), seem to be suffering from (I'm NOT an expert on this, and could be mistaken) severe autism and/or obsessive/compulsive behavior and/or learning difficulties and/or mental illness and/or the beginnings of dementia.This seems to centre around an extreme obsession, with "their" Nintendo Games DVD collection. Which seems to be the heart and sole of their life.Sadly, they seem to get into some kind of extreme panic attack and/or compulsion and/or obsession and/or insert-name-of-disorder. Which possesses them to wildly worry about the slightest/tiniest risk to their beloved Nintendo DVD collection (or vaguely similar).This means that they seem to go on intense rituals, where they constantly/regularly check for the slightest sign, that their beloved DVD collection, is going to get data rot, in the next 15 years or so. (Hence historic threads, about slight gaps in DVD cases letting light in and destroying data, Fungi attacking DVD plastics, Electrolytic Capacitor Life, How to Preserve Electronics In Sealed Ziplock bags, DVD alignment testing, BadBlocks and other HDD symptoms of data integrity failure etc etc).Unfortunately, they have been actively using the internet (an apparently bewilderingly huge number of Forums), to (sadly) repeatedly/compulsively ask the same question, again, again, again, again, again, did I remember to say "Again and Again".Across a wildly huge number of different forums, repeating identical or very similar, apparent text pastes, in the same thread, and multiple similar/identical threads, on those forums.Often, usually/ultimately resulting in moderator warnings/suspensions and then outright bans.E.g. (This thread, seems to be part of the "I just used S.M.A.R.T. and didn't properly understand it", and have gone into a huge panic, because the recovered sector count was non-zero (potentially entirely normal/acceptable on a very old disk drive), on an ancient HDD drive, from around the year 2000).Quote from: classicsamus87 on December 16, 2020, 08:19:43 pmI don't know if suggesting you find a Psychiatrist/Psychologist/Doctor/Knowledgeable-Friend-or-Family member, who can make you feel a lot better about these issues. E.g. with Cognitive Behavior Therapy.To all moderators:There doesn't seem to be an obvious solution. In some cases (where this user was left, unbanned and relatively unrestricted), users ended up getting so fed up, they started attacking this user, with swear words and possibly worse. (I'm uncertain, as such remarks were probably historically deleted).tl;drThey don't seem to be able to comprehend answers (properly/usefully), and just seem to keep on, most often just apparently copying and pasting the same text (or similar), all over the internet.

author: Halcyon
author_rank: Unknown
timestamp: December 17, 2020, 09:00:04 am
content: Quote from: classicsamus87 on December 16, 2020, 01:12:39 pmRegistering on a forum doesn't prove anything. We get all manner of automatic spam-bots here (yes, it's a real thing).How about by starting out by telling us a little about yourself? (Maybe in another thread, so not to de-rail this one). People would be much more open to helping if they know a bit about who is on the other end of the keyboard. Just say hi, treat it like a normal every day conversation.

author: Nominal Animal
author_rank: Super Contributor
timestamp: December 17, 2020, 09:35:15 am
content: Quote from: MK14 on December 17, 2020, 12:31:03 amI concur. In particular, I detect no malice or intent to derail or annoy anyone, just a deep need to find answers, but difficulty expressing the question and accepting an answer. I wish I could help.I even tried to help them understand via a few private messages, but had to stop and block them, because of my own frustration at the communications difficulties. I could detect myself losing patience, and that does not help.I do feel compassion, because the root cause is an affliction; but – and I am saying this as someone who has required psychiatric help themselves for recurring depression – classicsamus87 themselves are the only one who can seek help to try and deal with the communications issues, and more importantly, the core issues causing them anxiety and the need to repeat the same questions in an effort to get emotional closure.Personally, I considercognitive behavioural therapythe same for your mind, as going to a physiotherapy is after a physical injury. I don't know if it is applicable to classicsamus87 or if some other form would fit their needs better, but my point is, there is still a lot of misunderstanding what this kind of help is, causing many to reject such help for no good reason. I myself would have fared much better, if I had sought help a decade earlier than I did; and am still paying the price for that error. Do not be stupid like I was, please.

author: Mechatrommer
author_rank: Super Contributor
timestamp: December 17, 2020, 01:23:02 pm
content: he already got countless answer from countless members to his confusing question about his SMART things in countless threads and he keep spitting that shit again and again. i thought repeating things will get a member banned for good, even if he is a real human (usually ads) maybe he expect there is technology to recover bad data and he wont stop spitting shit until he found the non existence answer he expected. he can zip but he doesnt have a butt bone to test and compare data unzipped. somehow he passed the mod's emotional detector. imagine a 5 years old kid asking how to solve third order differential equations but expecting it can be done with simple +-/x. so he keep spitting shit until he find someone can do what he want.

author: ebastler
author_rank: Super Contributor
timestamp: December 17, 2020, 01:44:58 pm
content: @mechatrommer -- you may want to re-read the posts from MK14 and Nominal Animal, just prior to yours, and the "reassess directives".How about some empathy?

author: Mechatrommer
author_rank: Super Contributor
timestamp: December 17, 2020, 02:01:00 pm
content: oh i read Animal's post just before at the "i'm losing patience" phrase... maybe he can retry by replying one or two words simple answers to the "bot" and see if he can fix it. and oh i also read MK14's at the line of "Nintendo DVD nuts" he probably right or wrong, but i feel something terrible has happened anyway somewhere.

author: Ian.M
author_rank: Super Contributor
timestamp: December 17, 2020, 02:18:28 pm
content: Quote from: Halcyon on December 17, 2020, 09:00:04 am*IF* the O.P doesn't mind disclosing their country, I would suggest asking for a photo of the front page of a national or regional newspaper no more than three days old, with their user name written diagonally across it with a marker pen.

author: gnif
author_rank: Unknown
timestamp: December 18, 2020, 09:04:00 am
content: Just to be on-topic though, there are zero guarantees that corrupt data will not get burnt to DVD medium, or even copied across HDDs, etc...A ton of research goes into this topic for data security with mission-critical systems, an error can happen undetected in any number of places, from faulty RAM, or cosmic radiation causing bitflips, or electronic noise, causing undetected errors on the SATA link, just to name a few. Also, don't forget there is also RAM on the HDD itself that can also experience the same issues, it's not just your system RAM at play here.This is a good read:https://www.enterprisestorageforum.com/storage-networking/sas-vs-sata.htmlQuoteSDC = Silent Data Corruption (this is undetectable without CPU side checksums, etc)QuoteTechnologies like ZFS help with this as all the data is checksummed and scrubbed regularly to find and correct errors that may have happened, but this is only useful if you invest in the required technology to run such an array, such as ECC RAM, and ideally use SAS drives so link errors are detected and corrected.Data protection is a game of probability, nothing is definite.