We help IT Professionals succeed at work.

Can I switch to Raid 1 from Raid 0 and not lose data?

Donnie616 asked
I have 2 HDD's in Raid 0.  They are 200GB each WDigital SATA drives.  They have very, valuable information on them.  I would like to know if I can and  how do I switch (if I can) to Raid 1 .  Would it be best to do it from the bios or from a very nice little utility called  VIARAID.  My controller is by Via and this tool came with the controller's driver.  I have read it inside out and want to know if I can switch to R1 from R0 with data on the drives. That is the one issue it does not mention but it does allow for the assumption on my part that It can be done  Can this be done safely and EASILY?  Bios or Raid tool? OR BOTH?

Raid 0 appears to me just a waste of good hdd space.  Is that right?

Thank you in advance,

Watch Question

Lee W, MVPTechnology and Business Process Advisor
Most Valuable Expert 2013

RAID 0 is actually the only form of RAID that is NOT a waste of space.  RAID 0 combines two drives into one logical drive that, in theory, performs better.  BUT, this increased performance comes at the price of reliability - if EITHER of the drives fail, you lose ALL data on BOTH drives.

With more advanced RAID controllers, it is possible to convert "on-the-fly" from RAID 1 to RAID 5.  However, because a virtual disk using RAID 0 is TWICE the size of the disk space presented by a RAID 1, I see no way you could do such a conversion without backing up the data and wiping out the drive and finally recreating the RAID.


Oh boy.  Now what?
Lee W, MVPTechnology and Business Process Advisor
Most Valuable Expert 2013

Backup your data and reinstall.

It's foolish to consider your data valuable and NOT have backups.


Leew- this drive IS my backup drive.  I just REINSTALLED today and it has been a nightmare for a week.  I am lucky that I have this drive. It backed up my C drive and I am reinstalling from many EXE files many, many utils, progs, and apps that I would otherwise have no access to.  This is not my boot drive and it never was.  I unplugged the drives and reinstalled Windows on Pata drive. I was just curious about the Raid 1 thing vs the raid 0 and I like the raid 1 idea.  I am not foolish if I do not know better.  AND if I knew better I wouldn't need you expert's as much as I do.  Computer illiterate yes!  But foolish?  And it is also backed up on an external usb drive for good measure. And by the way everything I said I just did has been from Expert's helping me for the past couple of years.  Yes even yourself.  But Foolish?

What did I do that was so wrong by using this as my backup?  When my winxp install became severely corrupted I started to put everything on this 400 gb drive. (2 X 200)

Lee W, MVPTechnology and Business Process Advisor
Most Valuable Expert 2013

It's not clear what you did or what you have.  I didn't call you foolish, but if you felt I did there's nothing I can do about that.  valuable data needs to be backed up.  PERIOD.  You didn't mention this was your backup until the last comment?

If this is your backup, then restore your data and then remake these disks a RAID 1.  But you also need to understand - RAID is not backup - RAID 1, RAID 0, RAID 5 - RAID does not protect you against corruption or accidental deletion.  It's redundancy to protect against single disk failure.  Again, if this is valuable data, then you should be storing this on a backup device (external hard drive) and taking it off site.  I've posted my backup comment probably close to 100 times here so if you've searched the site, you've probably read it... just because you aren't a business (or haven't directly indicated you are business) doesn't mean that most if not all of the concepts don't apply to you.

While generally agreeing with leew, here is what I would suggest based on the above discussion:

(a) Make a complete copy of your files from the raid-0 disk to a new disk (perhaps usb).

(b) Verify the copy is good. This is very important if you consider your data valuable.

(c) Verify that you have your files in three places: the C: drive, the raid-0 disk, and the newly created backup from step (a)

(d) Break the raid-0 set and convert to raid-1, reformatting if necessary.

(e) Copy your data back from to the new raid-1 disk.

Note that at no point during this process is our data on less than two disks. This rule should be followed for all valuable files, as a minimum.



OK; Peace.  Exactly what purpose does raid serve anyway? Does it prevent me from having to put the data in 2 separate places?  Does raid do that for me instead of me having to do it myself? For example If my Main C (Boot) drive has some photos that I need.  I copy them to a separate 200gb hdd(SATA).  Then I copy them one more time again on a second 200gb hdd.  Now I have it in 3 places separately.  Does Raid 1 do this for me?  What is the exact benefit of the raid 1 as opposed to the 2 separate drives ?  Especially if I have these photos on an external plug in device. as well.  Why can't I take what I need (which I have already done) and put on an external USB HDD.  I have had this raid 0 config for 2 1/2 years, knowing very little about Raid.  It seems to have been OK so far and It really came in handy with this last crash.  I just happened to notice in the bios and in my raid utility that came with the MB CD,  that raid 1 was different and it appears that it might be better to go that way.  this was actually a casual question wherein I would have switched to raid 1 because it seems better for me. But it is not an emergency, nor is it even neccessary.  These 2 discs have been for storage of stuff that I have had on my main boot hdd.  It duplicates the c drive, which I copied folders at a time and am now using to restore my system.

So if i did not have my 2 identical 200gb hdd's in raid 0 wouldn't it be batter to not have any raid at all?  with all my data in one of the drives and even having the 2nd one empty?  Am I correct to think that 2 X 200gb drives with no raid 0 is better than 400gb in raid 0?  It is a difficult concept for an old man to grasp.   I did not know raid was not backup.  I really didn't.  You both told me to remake this as a raid 1 when I finish with the ffiles.  WHY?  Why not just 1. leave it the way it is as a raid 0 like it has been or 2. make it 2 reguar 200 gb hdd's?  What would you do in my situation?  would you do what you both said above?  If so I will do the same, but I would want to know why?  I apologize for being so thick-headed, but I just do not understand.

I am going to post on the backup area as soon as I get all configured up again, because I really do not understand the hows and whys of that conncept moreso than this and that is more important than this I feel.  if these 2 drives were not in raid 0, the data would still have been there woudldn't it?

 This PC is personal with about 25% busines on it.  Here is what I have:

1.  Maxtor C drve 250gb.  It is my boot drive and contains windows.  It is now 4gbfull.  Just reformatted.

2.  2 X 200gb Wd SATA hdd's.  They(it) are currently in raid 0 containining 80gb of photos, , data,   and the Executable files to all of my apps, utils, and programs.

 I am slowly using the executables to reinstall my stuff after reinstalling winXP Pro

I just backtracked this question and  Leew you have scared me when you said that I would lose all my data if only one drive fails in this raid 0 thing as a price to pay for performance.


tHANK YOU FOR YOUR TIME and I am sorry I cannot seem to grasp the concept raid.


Donnie, as great experts like Leew and R-K said, I just like to answer some of your concern, there can be many good reasons for using RAID. A few are; the ability to combine several physical disks into one larger "virtual" device, performance improvements, and redundancy. It is, however, very important to understand that RAID is not a substitute for good backups. Some RAID levels will make your systems immune to data loss from single-disk failures, but RAID will not allow you to recover from an accidental. RAID will also not help you preserve your data if the server holding the RAID itself is lost in one way or the other (theft, flooding, earthquake, Martian invasion etc.)
RAID will generally allow you to keep systems up and running, in case of common hardware problems (single disk failure). It is not in itself a complete data safety solution. This is very important to realize.

As said above, you can not convert raid 0 as you have now to raid 1, there is no such support like that for you now. You will need back up data to external drive or DVD's, then break the raid 0 and then creating raid 1. Normally, in my experiences, I would setup raid 1 is OS or boot drive for in such case os corruption 1 drive, other drive in raid 1 will give a chance to keep the system running and replace the fail drive without stopping production. Also, I would setup raid 5 for data.

Also, for raid 1 setup, the link below is how-to:


Ok I think I get the point.  Are you following me Punky? Thanks.  three people said the same thing, so it looks to me that raid 1 might be suitable for me.  I know what I have to do to do that, but now another issue is raised that makes sense to me,  but How the ____ do I set up my windows install and boot drive on this as yet undone raid 1 config when I am already going well and happy in the single pata drive?   I do not think I can go through another reformat/reinstall right now.

You of all people should know the jams I can get myself into, Punky, you have been following and assisting me for 5 weeks.  You even got the prize yesterday, remember?  You of all people know that with Donnie, "things that make sense don't take off,  for I am so dense"  

So what is the procedure for putting the boot stuff on  raid 1 setup?  And are we sure that is the bset way to go?  

Thank you,

Technology and Business Process Advisor
Most Valuable Expert 2013
The information and link PUNKY provided may help you understand.  I'll try to explain again.

RAID - Redundant Array of Inexpensive Disks.  There are several different types of RAID.  The most common are RAID 1, RAID 5, and RAID 0.  The concept is to allow for one disk drive to fail and still keep running, not losing any data.  Now, RAID 0 is the only form of RAID that isn't really RAID.  If one of the disks fails, your data is lost - short of an expensive data recovery service.  This doesn't mean your data is doomed the instant you put it on a RAID 0 array - but it does mean that if one of the disks fails, you lose everything.  Hard disks fail.  They are fairly reliable (I have had one failure about 6 months ago, but other than that I haven't had any of my 15 or so hard drives fail on me in at least 2 years.  But they do fail.  They have moving parts and anything that moves can and does wear down.  Your RAID 0 WILL fail... odds are not for another couple of years or longer... but it could happen tomorrow - or 10 years from now.  But if you left it running, it will fail someday, just as your car's engine will fail some day.

Using any other form of RAID, you can deal with such a failure because the odds of BOTH drives failing is pretty low (but it COULD happen).  You would do so because if one of the disks failed, then the other(s) would still keep your data available and reasonably safe for a day or two until you replaced that disk.  Once replaced, it could "rebuild" the array and restore that redundancy, once again protecting you from a single disk failing.  Again, this is with any form of RAID EXCEPT RAID 0.

Now, all that said, RAID is not really a backup.  It is for the hardware, in case of hardware failure... but RAID cannot protect you from things like data corruption and accidental deletion.  Think about it - a RAID 1 is a mirror - that means it's an exact copy of the data on the other disk - and it's kept instantly up to date.  So if you accidentally delete a file, it's gone, instantly, from both drives.  

For backup, you need to be putting the data on another media that can be taken to another location.  Why?  If your house burns down, your data is almost certainly gone too - unless you have a copy of it at another location - your work, you're parent's house, a friend's place.

Here's the backup comment I referenced - I really recommend you read it.

As for what I would do, I would not use RAID 0.  The only time I would use RAID 0 is in conjunction with a RAID 1 (often called RAID 10 or RAID 0+1 - these essentially make RAID 0's safe by adding mirror (RAID 1) protection) or for data I really didn't care about.  For example, if I did video editing, I would keep the original videos on a RAID other than 0 and I would use a RAID 0 purely for "temp" space as I edited the file together.
Lee W, MVPTechnology and Business Process Advisor
Most Valuable Expert 2013

Something that's not clear to me...

I understand you have one physical disk that is your C: drive and is 250GB.

I understand you have TWO 200 GB drives that are configured in a RAID 0, most likely as drive D:.

I understand you have your programs largely installed to D: as well as important files.

Is the above correct?

Hi Donnie,

Punky has already explained the pros and cons fairly well. I am just restating them as answers to your specific questions in case it helps:

(1) "Exactly what purpose does raid serve anyway?"

Briefly, the common three types of raid and their purpose:
Raid-0 - allows you to treat two smaller disks and one big disk
Raid-1 - makes a mirror of one disk to another in real time
Raid-5 - Allows you to treat 3 disks as one, adding fault-tolerance so you can recover from the failure of any one of those disks.
(the above is greatly simplified, of course)

Keeping the above in mind, Raid-0 should be used in cases where the files are already backed up somewhere else, or for working storage where you don't care about data loss. Raid-0 has the greatest risk of data loss because the loss of any one disk means all data are lost. Raid-0 does not seem suitable for your case.

Raid-1 can be handy for backing up the system disk, because it allows for fastest recovery. In case either of the disk fails, you simply keep going with the mirror disk. In some cases it may be handy also for the data disk, if you don't have another backup. But it is not the best solution for data backup. More on that below.

Raid-5 is sort of a cross between raid-0 and raid-1. The data are spread across three disks, and if any one of those three fail, you can replace it and rebuild the raid. It is not as fast to recover as raid-1 because you have to spend the time rebuilding and replacing etc. It is more space efficient (than raid-1) because you get the capacity of 66% of the sum of the three disks (vs. 50% with raid-1 and 100% with raid-0).

(2) "Does it prevent me from having to put the data in 2 separate places?"

The short answer is No. Raid-0 of course provides no backup, but even raid-1 or raid-5 should not be considered the complete backup solution. What raid-1 and raid-5 do protect you from is a hard disk crash. But raid does not protect you from other possible problems such as (a) You accidentally delete some files - since raid works in real time, the files will be gone immedialtely from both disks (b) All eggs in one basket problem - if your computer suffers physical damage, such as fire, water, theft etc. then both raid disks will be lost.

Therefore I highly recommend having backups in another separate location, preferably in separate buildings. This can be achieved with a usb drive or writeable CD's or DVD's (more on that below).

(3) "What is the exact benefit of the raid 1 as opposed to the 2 separate drives ?"

Assuming you mean two separate drives in the same computer, the advantage of separate drives is that if you accidentally lose one of your files from one disk, you can still recover from the other, while in raid-1 they would both be lost. The downside of separate disks is that you have to remember to make the backups, say once a day, though this can be easily automated with a scheduled batch job. This is the approach I use myself.

(4) "Why can't I take what I need (which I have already done) and put on an external USB HDD?"

This is an excellent idea, esp. if you remember to do it regularly, as much as daily if possible, and then put the usb drive in a separate safe location. Again, if you create a batch file that only copies files that have changed since the last copy, you can reduce the time per backup to just 5 mins or so.

(5) "So if i did not have my 2 identical 200gb hdd's in raid 0 wouldn't it be batter to not have any raid at all?  with all my data in one of the drives and even having the 2nd one empty?  Am I correct to think that 2 X 200gb drives with no raid 0 is better than 400gb in raid 0?"

In your case, yes. The amount of data you have does not need a 400 GB drive, and 2 x 200 GB drives are half as likely to fail as a raid-0 setup that combines the two. The only downside is that to break the raid-0 setup now and make them separate disks will take some time but it will be safer in the long run.

Based on your description, I would suggest the following (though there is not always one "best" way):

(a) Drive C: - use it for system, all programs, and some data.
(b) Break RAID-0 mirror, and treat the two drives as separate. Use the first one for most of your data, and the second as one where you can backup everything from the first with a daily scheduled job. You can also include backing up useful folders from c: to this extra drive in the daily backup.
(c) Consider getting an external usb drive - a 500 GB model is in low $100 range now, and use that for a backup that you can store in a somewhat separate location.
(d) For things that don't change often, such as photos, write them to CD's or DVD's for extra backup.

When you create CD's or DVD's, do a spot check to make sure you can read the files back, optical media tends to be less reliable than hard drives. Preferably do this spot check on another computer.  Also, never use the RW media (CD-RW or DVD-RW) for long-term storage, much safer to use CD-R or DVD-R. Finally, make two copies of each optical disk, and store one of them "off site".

One important thing with optical disks is to use a good numbering system, and keep a "catalog" on your hard disk of what each CD/DVD contains. Otherwise it becomes very hard later to locate files when you need them.

If you're interested in specifics, such as how to "catalog", or what batch job to use for daily backups, please write back.

If you want to follow the path of least work, then I would suggest:

Leave your C: drive and Raid-0 setup as is, but: (a) Add a daily backup of data to external USB disk plus (b) Add occasional archiving of esential files to CD/DVD.

Seems I rambled on too long and probably repeated things already said by leew and punky, sorry, but inadequate or improper backup is something that is all too common these days, and I am very glad you're asking these questions _before_ all has been lost due to a disk crash.


Sorry leew, did not know you were posting at the same time, I was just slow in typing and hitting that submit button!


Leew: my setup now is 250gb hdd as main drive.  for years 2 1/2 years I used the 2 x 200 raid 0 as a place to store everything important NOT including programs.  If I downloded an EXE file from the internet, I clicked it to instal the program on C drive.  Then I dragged and dropped a copy of it to the raid drive where it now sits so I can reinstall it now that I lost all of my programs on C through a neccessary Reformat, that coincidentally Punky guided me through because I had problems even with that.  In the D drive is also evrything important, so as you have just taught me, I have to back it up the right way, then clear out the drives and make them a raid 1. But thankfully I put them there even thought it was notr the correct way to backup.

If I lost The raid drive now, it would be bad.  If I lost it 6 weeks ago, nothing would matter.  I also have a USB External drive that is a duplicate of the old C and the current D.  

What I really need to learn is how to correctly use a backup program but I have a lot of reading to do thanks to you all.  let me do som studying and get back to you after I read up.

thank you all for your input, altho it is a lot to take in, you guys are great.



The website provided by leew is great but I will need time to study and return to E_E on the backup section bcause as r=k said I am guilty of improper backing up.  I  do not know wha to do with  or how to correctly apply a daily automatic backup.  I do have them but when the time comes I will ask that in another question, however I am interested in learning about "batch jobs" before this question  on raid is closed.


Donnie :)

Have fun reading! even there is a lot of information in written here by R-K and Leew, which are always great to copy them and save in my knowledge bases!

I am not following you. The EE new website with Alert setup that gives my email box has it meaning now "you got mail" (before I have about few emails a day, now few hundreds of them but not junks or spam). Your question has poped up in email and so I am here again to see you :) . I know EE board around 2003, and been sit back to read comments from experts couple of years before starting to input my own comments. This is great place to learn (that helps me save a lot of money to buy books or spending time in school again for ... I am too old for school :) .


I didn't realize you had website reference.  Thanks.  I was just teasing you about follwing me.

I have a lot of studying to do, so I will go now and return much later.  I have to read carefully because one missed word in my case could mean disaster, like clicking yes when I mean no.  A real example is I was able to finally make a good slipstreamed version of winxp with sp2 INCLUDING  all hotfixes and many drivers. But it just would not work. The result was me trying to boot with a non-bootable disc and crying to you guys tht my pc was messed up, until it was suggested I try another disc.  I missed the instructions about extracting the Microsoft Corporation .img, so disc after disc would not boot simply because I read too sloppily.  Speaking for me, I must read very slowly and carefully or I screw up.

You guys are all great.  See you later.

thanks,  d616


I have gleaned all the info I need from you all and your refferal sites.  Thank you all.  it is difficult to pick a winner especially when all comments were highly informative.  i have things to tend to away from the PC today, so I will have time to think about an intelligent descion with regard to that.

At thee time of the first backup job, I will be back if I have problems.

r-k: What about the "batch job" info you offered?

Thank you all again.


Here is the batch job I suggested earlier:

(Assuming you have set-up a drive dedicated to backups, named the Z: drive, and you want to backup everything from the C: and D: drives to the Z: drive, leaving out certain files like program files and temp files etc.)

(1) Create a folder named c:\backup on the c: drive

(2) Copy the following lines into a text file with Notepad and save that into the c:\backup folder and give it the name "backit.bat":

-----cut here----------
Rem Copy all files modified since last backup to another disk
Rem       /s  means all subdirectories also
Rem       /e  means empty folders also
Rem       /c  means ignore errors
Rem       /f  means full display in console window
Rem       /h  means hidden files also copied
Rem       /d  means copy only those files that have changed
Rem       /y  means do not prompt for overwriting existing files
Rem       /o  means retain file ownership and acl info

xcopy c:\*.*   /s/e z:\backup-of-c\   /c/f/h/d/y/o /EXCLUDE:exclude.txt
xcopy d:\*.*  /s/e z:\backup-of-d\   /c/f/h/d/y/o /EXCLUDE:exclude.txt
------cut here-------

(3) Create a new text file with Notepad and copy-and-paste the following two lines into it. Then save it in the c:\backup folder with the name "daily.bat"

cmd /c "c:\backup\backit.bat" > "c:\backup\backit.log"

(4) Create a new text file with Notepad and copy-and-paste the following lines into it. Save it in c:\backup with the name "exclude.txt"

----------cut here-------------
\Temporary Internet Files\
\System Volume Information\
\Program Files\
----------cut here-------------

As you might guess, the list in exclude.txt is of files and folders you _don't_ want backed up. This is just a list I use sometimes, you should feel free to add or subtract from it.

(5) Create two folders named z:\backup-of-c and z:\backup-of-d on your z: drive. These will hold the backed up contents.

(6) Schedule the file named "daily.bat" to run once a day. You can do this with Control Panel -> Scheduled Tasks -> Add Scheduled Task -> Browse etc. Pick a time when the computer will be on but you will not have applications open.

Alternately, you can choose not to schedule it, but just create a shortcut to "daily.bat" on your desktop and double-click on it when you need to do a backup.

The first time the backup runs it will take an hour or two, but subsequent times it should take 5 to 10 mins max because only those files that changed will be copied.

It is very important to check the results of the backup (i.e. examine the files on the z: drive) at least the first few times and periodically thereafter, to make sure the backup is doing what you expected. Also look at the backit.log file for a quick check.

Second, this backup does not backup files that are "in use", and worse, may even remove the old copies from the z: drive, so it is very important to quit applications like Word, Photoshop, eMail etc. while the backup runs. Web browsing is OK.

This simple backup never removes files from z: (even if you delete them from c:). In some cases this is a plus because you may need some old file later. In other cases it is a minus because the z: drive may get cluttered with obsolete files. If the latter is a problem then one simple solution is to simply delete everything from z: when it becomes too full. The next backup will make a clean copy. Alternately you can use some other backup method.

If you want to name your backup drive something other than z: just edit the two lines that refer to z:

If you wish to do backups while files are open then I would not recommend the above - use NTBackup in that case.

Post back with any questions. Hope I did not leave out any important detail.