Home News Reviews Forums Shop


Buying a CD-RW for backup?

Burn baby burn!

Buying a CD-RW for backup?

Postby technut on Tue Mar 18, 2003 8:04 am

Hi everyone. I have never owned a CD-R or CD-RW drive, so please bear with me.

I am wonder if CD-R or CD-RW is reliable enough to use for data backup. As you know, for backup purposes, there cannot be a single error (even a single bit being off could corrupt the data). This is unlike music recording where a few misplaced bits would probably not be noticed. Is the integrity of CD-R sufficient for data backup? What about CD-RW?

I have heard that Lite-On is one of the best manufacturer's of CD-RW drives. So I read the review on this site of the new Lite-On 52x24x52 drive. The review indicated that quite a few data errors were encountered. From my limited knowledge, it sounds like these errors could possibly corrupt data either when being written, or when being read. Or did I misinterpret the review?

Would this Lite-On 52x24x52 CD-RW drive be the best choice for data backup purposes, or is there a better quality (more reliable) drive that would better suit my requirements? I simply want to buy a drive that will ensure that my data is backed up without a single error, and can be read back in without a single error.

Thank you in advance for anyone with the knowledge and experience to respond.
technut
Buffer Underrun
 
Posts: 7
Joined: Tue Mar 18, 2003 7:15 am

Postby TheWizard on Tue Mar 18, 2003 8:50 am

Get any decent burner: LG, Lite-On, Samsung, Yamaha, Plextor. Then burn with quality media found in this list - http://www.cdrlabs.com/phpBB/viewtopic.php?t=6005

Usually, the lower speed you burn at, the less chance there will be errors. For example, not much blank media burns at 52X in the newest burners, so burn slower. Don't be afraid to burn very slow, we're talking snail speed like 8X, to ensure error-free results.
No, I like women.
TheWizard
CD-RW Player
 
Posts: 2074
Joined: Fri Jun 28, 2002 6:56 pm

Postby cfitz on Tue Mar 18, 2003 11:23 am

CD-R technology for data applications includes three levels of error detection and correction, making CD-Rs a robust and durable backup choice. Of course, they are not indestructible and must be treated with proper care. For example, do not expose them to bright light for long periods, do not expose them to excessive heat or humidity, and protect them from scratches. In addition, there are numerous tools such as CD Doctor, CD Speed Scan Disc and CDCheck that allow you to monitor the condition of your backups to ensure you can detect and correct any degradation long before it becomes fatal.

Personally I think CD-Rs in particular and optical media in general are more durable and better suited for long-term storage than magnetic media such as tapes.

cfitz
cfitz
CD-RW Curmudgeon
 
Posts: 4572
Joined: Sat Jul 27, 2002 10:44 am

Postby CowboySlim on Tue Mar 18, 2003 11:57 am

tecnut,

You may want to look at the Yamaha CRWF1. It is a little slower than the fastest Lite-Ons and costs a little more. However, it comes bundled with a great S/W package that meets your needs. It has the Ahead burning S/W which most consider the best. It also comes with Dantz Retrospect Express, a superior backup and disaster recovery package. I have used Dantz for both backup and restore/disaster recovery without a problem. It includes error checking and correction for perfect data restores.

Good luck,
Slim
User avatar
CowboySlim
CD-RW Player
 
Posts: 1868
Joined: Tue Jan 28, 2003 3:58 pm
Location: Huntington Beach, CA

Postby UALOneKPlus on Tue Mar 18, 2003 2:32 pm

I fully agree with cftiz - Burning CD-R's is the only way for me to back up data.

The only other full proof way to easily back up data, is to buy a spare hard drive and back up your data to there - but it's not very portable unless you use Firewire or USB 2.0.
User avatar
UALOneKPlus
CD-RW Player
 
Posts: 1082
Joined: Sun Jan 05, 2003 8:28 am

Postby tazdevl on Tue Mar 18, 2003 5:00 pm

Too much data here. I need Blu Ray :D...

If you have a lot of data, DVD is a nice altenative to CDR. Backing up my MP3s alone takes 25 CDRs.
RIG:
P4 2.6C, Thermalright SP94/Panaflo 92MM M1A, IC7 Max3, Swifty MCX159, 1GB Geil PC4000 Ultra Plat, Radeon 8500, Audigy 2, 2X WD Raptor RAID 0, WD 250GB SE, Plex 708A, 166SDVD, LianLi PC75, XP Pro.
User avatar
tazdevl
CD-RW Player
 
Posts: 979
Joined: Tue May 14, 2002 11:03 pm

Backup Software

Postby seafoodplate on Wed Mar 19, 2003 10:22 am

I have a lot of clients ask the same question and it really has to do with the amount of data you have as listed above.

Also, if you are looking for a good, easy backup program try Handy Backup at www.handybackup.com.
seafoodplate
Buffer Underrun
 
Posts: 2
Joined: Tue Mar 18, 2003 10:31 am

Postby jase on Wed Mar 19, 2003 11:20 am

I see no reason why DVD/CDR shouldn't be used for data backup.

Even the cheapest of media currently available on the cheapest of drives should be capable of being written at 16x with no errors on the disc that can't be corrected by any reader. Using good quality media on a good writer should guarantee a very secure backup.

As for longevity, well there is a good chance of no data corruption after 5 or 10 years with good media. This is at least comparable with tape.
jase
CD-RW Player
 
Posts: 965
Joined: Fri Sep 21, 2001 8:00 pm

Postby technut on Mon Mar 24, 2003 1:15 am

[quote="cfitz"]Personally I think CD-Rs in particular and optical media in general are more durable and better suited for long-term storage than magnetic media such as tapes.

cfitz[/quote]

Thanks to everyone who took the time to reply! All your responses were very useful. So many smart people here!

It seems everyone is saying that any drive with any reasonable-quality media will give a good error-free backup. That's great to hear. But what I don't understand is why the review (by this site) of one of the most recommended drives (the Lite-On 52x24x52) indicated that all sorts of errors were encountered on some brand name media. This seems contrary to what everyone is saying that any drive will produce error-free results. Obviously, I'm not understanding something! :oops:

When it comes to backups, you don't want even a single bit to be in error, and the review on this site of the Lite-On indicated that many errors were encountered. So I would think that it wouldn't be a good choice for backups. But everyone seems to be saying the opposite, so what am I not understanding?

Thanks for your patience!
technut
Buffer Underrun
 
Posts: 7
Joined: Tue Mar 18, 2003 7:15 am

Postby cfitz on Mon Mar 24, 2003 11:33 am

Those errors are corrected in the drive before the data leaves the drive.

There are three levels of error detection and correction for data CDs. The nature of recording to optical media guarantees there will be errors, so the designers built in these levels of error correction to make sure the final data presented to the user is error-free. What you see in the test results are errors prior to correction. The test results are still useful, because the harder the drive has to work to correct existing errors on a disc, the less margin there is for handling new errors introduced by aging, scratches, etc.

By the way, your hard drive includes error detection and correction technology as well. Similar to CD-R recording, at the lowest levels where the bits are recorded on the disc's platters, errors are inevitable on hard discs as well.

cfitz
cfitz
CD-RW Curmudgeon
 
Posts: 4572
Joined: Sat Jul 27, 2002 10:44 am

Postby mmesker on Mon Mar 24, 2003 11:46 am

mmesker wrote:Backing up my MP3s alone takes 60 CDRs.


Fixed it for me.

I've owned two TDK drives (an 8x and a 48x) and never had a problem burning at the top speed with either of them. *shrugs*
mmesker
Buffer Underrun
 
Posts: 2
Joined: Sun Mar 23, 2003 4:54 pm
Location: Dekalb, IL

Postby technut on Wed Mar 26, 2003 4:47 am

cfitz wrote:Those errors are corrected in the drive before the data leaves the drive.

There are three levels of error detection and correction for data CDs...
cfitz


Thank you for all the great info! So much to understand about this medium.

I see you talking about C1 and C2 errors. I assume this is two out of the three types (or am I way off?). What is the third type of error detection and correction? Is there a good simple explanation of C1 and C2 errors?

A few more questions, if everyone is ok with it :lol:

When you write to a CDR or CDRW, is it immediately obvious that the information will be readable? I guess this is a 2-part question: (1) when using a specialized app to perform the writing, will it say "errors encountered... toss this disk?" (2) What if Windows XP itself is doing the writing (by just dragging and dropping files onto the drive); will it correctly tell you if errors were reported during the write?

Does the writer know that the info will be readable (in other words, does it try to read it back), or is it up to the user to then run a verification program to verify that each file can be read? I suppose it would be a better choice to actually verify that the info written to the new CDR/CDRW actutally MATCHES the source data (which is more than just verifying that SOMETHING can be read). This would involve a program to compare each file on the target to the source.

Is it standard practice of people using CDR's or CDRW's to use an app to verify data integrity (checking that each target file actually matches each source file), or is the reliability so good now that once a CD gets burned, you know without question that it is both (a) entirely readable and (b) the data on the CDR/CDRW actually matches the original source?

A few more questions... if you don't mind... although I fear that I may be asking too many :oops: !

When you write a CDR or CDRW, is it standard for there always to be these low level errors (later corrected by the error correcting process)? In other words, are CDR's or CDRW's ever (in reality) burned without low level errors, or do they all have them? Is the error correction used reliable enough that, unless scratched or otherwise damaged, the CDR or CDRW can be used as a reliable backup tool? Or do some of these low level errors translate to actual read errors that prevent data from being read correctly?

Which brings me to my next to final question: would the user know if the error correction did not properly correct a low level error? Or would the user only discover it later when he/she found the data to be corrupt?

(As an aside, with a floppy disk, if a sector cannot be read properly, the user sometimes will be told (sector error reported by the o/s), or sometimes (I believe) the data read will contain erroneous data (which is something I never liked about floppies).)

Finally (yea! :D ), when writing to a hard disk, if a bad sector is encountered, the drive will mark the sector as bad and not attempt to write to it again. Do CDR's and CDRW's do the same thing?

Well, I'm going to end my questions there! I hope I haven't pushed the limit too far :) . I was going to make it separate posts, but I figure since it's all one topic, it's simpler to keep it as a single thread. Many thanks to those who possess the amazing knowledge required to respond! :D
technut
Buffer Underrun
 
Posts: 7
Joined: Tue Mar 18, 2003 7:15 am

Postby cfitz on Wed Mar 26, 2003 9:35 am

technut wrote:I see you talking about C1 and C2 errors. I assume this is two out of the three types (or am I way off?). What is the third type of error detection and correction? Is there a good simple explanation of C1 and C2 errors?

At the most basic (and this really oversimplifies and glosses over a lot), the C1 layer corrects the most common errors, the C2 layer corrects "bigger" errors that make it past the C1 layer, and the third layer that is included in mode 1 and mode 2 form 1 discs consists of extra data bytes used for EDC/ECC. It corrects errors that get past the C2 layer. In an audio disc the drive will attempt to mask errors that get past the C2 layer by guessing what the correct value should be. More reading material may be found here:
http://www.roxio.com/en/support/cdr/cderrors.html
http://www.cdpage.com/dstuff/BobDana296.html#3
http://www.mscience.com/faq13.html
http://www.cdrlabs.com/phpBB/viewtopic. ... 6820#46820
http://www.cdrlabs.com/phpBB/viewtopic.php?t=8194
(a little more specifically, http://www.cdrlabs.com/phpBB/viewtopic. ... 6820#46820 )
http://club.cdfreaks.com/showthread.php ... adid=61943

technut wrote:When you write to a CDR or CDRW, is it immediately obvious that the information will be readable?

You can test to verify that the disc is good immediately after burning by making use of a variety of programs such as CD Speed, CD Doctor and CDCheck.

technut wrote:Does the writer know that the info will be readable (in other words, does it try to read it back), or is it up to the user to then run a verification program to verify that each file can be read?

You can do either or both. Burning programs such as Nero contain a "verify data" option that reads back the data from the freshly written disc at the end of the burn. You can also compare it yourself to the original data using programs such as CDCheck or MD5summer. All of the programs I have listed here (with the exception of the "verify" option in Nero Burning ROM itself) can be used at any time after a disc is burned, whether that is minutes later or years later.

technut wrote:I suppose it would be a better choice to actually verify that the info written to the new CDR/CDRW actutally MATCHES the source data (which is more than just verifying that SOMETHING can be read). This would involve a program to compare each file on the target to the source.

Again, the verify option, CDCheck and MD5summer, among others, do this. Furthermore, barring a bug in the writing program, a disc that is readable does guarantee that the data matches.

technut wrote:Is it standard practice of people using CDR's or CDRW's to use an app to verify data integrity (checking that each target file actually matches each source file), or is the reliability so good now that once a CD gets burned, you know without question that it is both (a) entirely readable and (b) the data on the CDR/CDRW actually matches the original source?

That depends on each individual and his or her comfort level. I often do, but not always. It depends on how critical the data are.

technut wrote:When you write a CDR or CDRW, is it standard for there always to be these low level errors (later corrected by the error correcting process)? In other words, are CDR's or CDRW's ever (in reality) burned without low level errors, or do they all have them?

Yes, it is inevitable that there will be some errors at the lowest level (C1). As I said in previous posts, the designers of the technology anticipated this and designed in error detection and correction to account for it. Let me ask you, do you trust the pressed CD-ROM discs from which you install your software? The CD-R discs I burn are far better quality with lower error rates than most of the pressed CD-ROM discs I see. By the way, the error detection and correction used on CD-R discs is the same as used on commercial pressed CD-ROM discs.

technut wrote:Is the error correction used reliable enough that, unless scratched or otherwise damaged, the CDR or CDRW can be used as a reliable backup tool?

Yes, yes, yes! Why do you refuse to believe us? And in fact the error correction is reliable enough that even with scratches (assuming they aren't too extensive) the data can be read back with 100% accuracy. Of course, things can go wrong, as with any technology, and some media and drives don't do as good a job as others. But you have been given the tools to protect yourself against this eventuality. You can use the listed software to test your own discs, and you can read these forums to find out what drives and media are better quality. Before you ask again, spend some time thoroughly reading these forums and the various reviews.

technut wrote:Which brings me to my next to final question: would the user know if the error correction did not properly correct a low level error? Or would the user only discover it later when he/she found the data to be corrupt?

If the disc can't be read due to errors, you will get a read error. It won't just quietly sneak by and show up as corrupted data that appeared to read correctly. There is some infinitesimally tiny chance that the errors would just happen to corrupt the data in such a way that the error could not be detected, but that is not a realistic fear.

technut wrote:Finally (yea! :D ), when writing to a hard disk, if a bad sector is encountered, the drive will mark the sector as bad and not attempt to write to it again. Do CDR's and CDRW's do the same thing?

The question is irrelevant for CD-R discs since they can only be written once. Such mapping is done with packet writing software on CD-RW, depending on the packet writing technology used. However, that is one aspect of recordable technology that I don't recommend. CD-RW media in general is less reliable than CD-R, and packet writing even more so. Some people have great success with it, but others have lost data due to bad packet-writing software or defective CD-RW discs.

cfitz
cfitz
CD-RW Curmudgeon
 
Posts: 4572
Joined: Sat Jul 27, 2002 10:44 am

Postby technut on Thu Mar 27, 2003 4:04 am

Thank you so much for all your great answers! Man, do you know your stuff! I printed out your post, and will use it as a GREAT reference! THANK YOU!

Just some very minor follow-ups...
cfitz wrote:If the disc can't be read due to errors, you will get a read error. It won't just quietly sneak by and show up as corrupted data that appeared to read correctly. There is some infinitesimally tiny chance that the errors would just happen to corrupt the data in such a way that the error could not be detected, but that is not a realistic fear.

Does it depend on the app whether or not read errors will be shown, or are they low-level o/s errors that are shown regardless of the app that encounters the errors?

technut wrote:...when writing to a hard disk, if a bad sector is encountered, the drive will mark the sector as bad and not attempt to write to it again. Do CDR's and CDRW's do the same thing?

cfitz wrote:The question is irrelevant for CD-R discs since they can only be written once...

Do they simply skip the bad sector (marking it as bad), and move on, or do they cancel the entire write operation?

BTW, I find your dicussion of CDR vs. CDRW to be very interesting (and unexpected due to my lack of experience with this storage medium). It's clear that you absolutely trust the reliability of CDR output (and for good reasons, as you point out), but don't really trust the reliability of CDRW output. Is that a fair analysis of your position, or am I taking your concerns about CDRW to a level higher than you intended?

Again, thanks so much for answering my previous post. I know I learned a tremendous amount from your comments, and I bet a lot of other people benefitted as well! :D
technut
Buffer Underrun
 
Posts: 7
Joined: Tue Mar 18, 2003 7:15 am

Postby cfitz on Thu Mar 27, 2003 11:27 am

technut wrote:Does it depend on the app whether or not read errors will be shown, or are they low-level o/s errors that are shown regardless of the app that encounters the errors?

The OS itself will fail to read the disc. How the application presents that fact to you depends on the application itself. You may get error messages like "read error" or "bad file" that are relatively easy to associate with a problem on the disc, or they may hide it in a higher level message like "could not display photo" or, if it is a poorly written application it may hang or crash. It all depends on how the authors of the application chose to handle file I/O errors.

technut wrote:Do they simply skip the bad sector (marking it as bad), and move on, or do they cancel the entire write operation?

If Nero fails during a portion of the writing process it will abort the entire operation. I haven't tried every burning program, but I imagine they all do the same.

technut wrote:It's clear that you absolutely trust the reliability of CDR output (and for good reasons, as you point out), but don't really trust the reliability of CDRW output. Is that a fair analysis of your position, or am I taking your concerns about CDRW to a level higher than you intended?

That is my personal position. I know that there are people who have had good success with CD-RW over the years, but I have personal had some bad luck and thus avoid it. This is particularly true when using CD-RW in conjunction with packet writing software, which tends to be buggy. I personally recommend using CD-RW for temporary storage and file transfer applications only, where the disc does not contain your only backup of valuable information.

cfitz
cfitz
CD-RW Curmudgeon
 
Posts: 4572
Joined: Sat Jul 27, 2002 10:44 am

Postby technut on Fri Mar 28, 2003 4:19 am

Thanks for the wealth of information cfitz! Absolutely great stuff!

technut wrote:Do they simply skip the bad sector (marking it as bad), and move on, or do they cancel the entire write operation?

cfitz wrote:If Nero fails during a portion of the writing process it will abort the entire operation. I haven't tried every burning program, but I imagine they all do the same.

Wow, that's pretty harsh. But in some ways its good because if a new disc has an unreadable sector, it may have more that are almost as bad (but not quite as bad... yet!). Your experience is obviously different from how a floppy disk is handled (a bad sector is just mapped out to be not used).

cfitz wrote:That is my personal position. I know that there are people who have had good success with CD-RW over the years, but I have personal had some bad luck and thus avoid it. This is particularly true when using CD-RW in conjunction with packet writing software, which tends to be buggy. I personally recommend using CD-RW for temporary storage and file transfer applications only, where the disc does not contain your only backup of valuable information.


That's real interesting. When CDRW drives came out, I thought it looked like such a great improvement over CDR drives... but now it seems like some knowledgeable people (such as yourself) don't really get much use out of the RW functionality.

Of course, CDR discs are cheap compared to CDRW discs, but if you are going to be writing to the same disc more than a few times, the CDRW discs become much more economical over time.

I thought the only problems with CDRW was when used with packet writing software. Before reading your post, I thought if you used CDRW in non-packet writing mode, that they were just as reliable as CDR's. Your post seems to indicate that is NOT the case (in your experience, at least, which seems to be based on quite a bit of expertise). (Note to others: if you respectfully have a different opinion, it would be useful to hear it! cfitz has great knowledge and experience, but it's always useful to hear other opinions, including different ones.)

I hesistate to make a suggestion, because you obviously have much more knowledge than I do, but I'm going to mention it because I think it might be useful to you. Try giving CDRW another chance using more current technology. Why? Because, like you, I've dismissed dozens of technologies as being too unreliable or unstable. But after the technology stabilized, it became reliable (and I was left out from using it due to my no longer valid experiences and bias). Now, if your bad experiences with CDRW ARE with current technology (say, a drive and media less than 6 months old), then you've already done this. :D

Again, many thanks for your wealth of information, and for your willingness to share a small piece of it!
technut
Buffer Underrun
 
Posts: 7
Joined: Tue Mar 18, 2003 7:15 am

Postby cfitz on Fri Mar 28, 2003 11:14 am

As I said, others have used CD-RW with good luck. I'm not making a blanket condemnation of CD-RW. And, as you suggest, one's chances of success improve if one burns ISO 9660 discs rather than packet writes.

For me personally, I have been telling myself for a couple months that I should get some of the Verbatim CD-RW and give them a try since many recommend them. So I haven't completely given up yet. However, I still would never use CD-RW for long-term backup or as the only media on which I store important data. There is the reliability issue, but even beyond that it doesn't make any sense to use an expensive rewritable disc effectively just once.

cfitz
cfitz
CD-RW Curmudgeon
 
Posts: 4572
Joined: Sat Jul 27, 2002 10:44 am


Return to CD-R/CD-RW Drives

Who is online

Users browsing this forum: No registered users and 0 guests

All Content is Copyright (c) 2001-2017 CDRLabs Inc.