I am setting up a storage solution in Windows where I wish to utilize the space on multiple physical drives and have them recognized as a single drive letter. I do not wish to do anything that places restrictions on how the space can be allocated, such as sym-linking, junctioning, or ntfs mounting one physical drive so that it appears to be a directory on another physical drive. For this reason I have decided to use a spanned volume to store some non-critical data.

Since this data is not critical, it would merely be inconvenient if some of it were lost. If all of the data were lost, that would be more inconvenient. This question is about avoiding inconvenience of said data loss and not about providing total data protection against a drive failure.

My question is: What real methods exist for recovering data from healthy physical drives on a spanned volume when one physical drive fails?

Unfortunately it is virtually impossible to google any information on this, as all that comes back are explanations that one should expect to lose all data should a physical disk on a spanned volume fail. Then the person who asked the question then realizes that they want to protect all their data, they are not interested in a spanned volume anyway, and no further information is revealed.

Please assume, until I prove otherwise, that I understand the details of what a spanned volume does, and the implications of using one, since this is not what my question is about.

I am optimistic that there are enough people who out of technical interest and curiosity will want to find out the answer to this question also!

Thank you for your help!

** Edit upon closing **

It's certainly possible that I misunderstood the mission of SO/SE/SF.

Just because something does not line up with YOUR use case does not mean there is not a use for it. Is this same point not made often enough when (often pointlessly) discussing a user's choice of software or operating system?

I'd like to thank MDMarra for not getting caught up in this. It is fun to have rep, but more importantly I am glad to have walked away with a real technical answer to my technical question. I did not know this before, even after a lot of time searching for information on this subject.

When searching for information on this question, 99% of the discussions and posts that one will find are explanations to novice users of the inferior data protection of spanned volumes... Usually followed by opinion pieces on why no one should use them, based on the assumption that all data recorded for all purposes is mission critical and cannot ever be lost.

Therefore, I knew going into this that my question could produce a strong and even emotional response from some people. I'm glad that one person felt that I asked a question with a finite and objective answer.

Hopefully the answer written here may go on to help the next person who has the same question about the technical properties of spanned volumes.

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    Use a proper and well-tested backup. Then you don't ever have to waste time worrying about this. – EEAA Jan 5 '14 at 20:04
  • @EEAA while that's certainly a best practice, but it's not useful or constructive to the question being asked. We're all taught that spanned data can be recovered, but never how. -- We're asking how. – BrainSlugs83 Mar 8 '16 at 5:27
  • It's posted as a comment, not an answer. – EEAA Mar 8 '16 at 5:49

Spanned volumes, unlike striped volumes, do not stripe data across all disks. This means that all data is written to the first logical disk in the span until it is filled, then additional data is written to the next logical disk, and so on.

This means that if a disk in a span fails, only the data that was written to that failed disk is gone. If you lost the first disk in a two-disk span, you'll lose the most data. If you lose the last disk in a span, you'll lose the least amount of data.

Any software capable of reading dynamics disks can get at data on remaining disks in a span, since whole files are stored on it - again, they are not striped across multiple disks. If this were a striped volume, this would not be the case. So, recovery of remaining files is very simple.

Recovery of files that were on the failed disk is a different story and would be the same as recovering data from a failed standalone disk. It depends on the what caused the failure.

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    Do you have any list of the tools capable of reading dynamic disks that you mention above? – noonand Nov 20 '14 at 15:16
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    Okay, and when the last disk in a spanned file system fails, how do you actually recover the data from the rest of the span? -- If you have a span of 8 disks, and one of them (the very last one) dies, what software do you use to get the data back? – BrainSlugs83 Mar 8 '16 at 5:23

I've had good luck in recovering data from failed drives in cases where the MFTs had failed sectors or were severely corrupted. This seems to be a fairly common kind of drive failure short of catastrophic (i.e., dead drive). The tool I use is for this is GetDataBack NTFS. It essentially analyzes all of the accessible sectors in the designated physical drive or volume to gather data needed to reconstruct the file indexes and saves a virtual MFT as a file on your PC. I can then see the entire file structure of the volume and am able to successfully copy all of the undamaged files to healthy drives. So, this should even work on a spanned volume where another (failed?) drive holds the MFT for its contents. But this could be a problem in the case of badly fragmented spanned volumes with files that have fragments that are not all on the same physical drive.

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