Hard Drive Problems/geneleal@yahoo.com

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Question
Hi, I have a general question about hard drives. When files or programs have been removed, corrupted, or simply deleted, just how gone are they. For example, when a file such as a document with personal information is deleted, where does it go. I'm just trying to learn more about this subject
as I become more familiar with computers.

Thanks,

Gene

Answer
Hi Gend!

When a file is stored on a hard drive, a file "header" is stored for that file, identifying the name and size of the file and where to find it, each block pointing to the next piece of the file.  This is an over-simplified model:

A0 header:  name=myfile.file, 4 blocks in size, start at A5
A1 HAMMER
A2 VERBOSE (B4)
A3 RILEY (C2)
A4 THIS (A5)
A5 IS (A8)
A6 SCREEN (G5)
A7
A8 MY (A9)
A9 FILE.
AA AFTER (AF)

So, if you check those blocks, you get:  THIS IS MY FILE.

Now, if you delete myfile.file, all that happens is that the "header" is deleted - the value of block A0 is set to null/blank:

A0
A1 HAMMER (end)
A2 VERBOSE (B4)
A3 RILEY (C2)
A4 THIS (start, A5)
A5 IS (A8)
A6 SCREEN (G5)
A7
A8 MY (A9)
A9 FILE. (end)
AA AFTER (AF)

So, the data is still there, but there is no longer a way to find it, since the header (containing the name, size, and starting location of the file no longer exist).  "Undelete" programs scour the drive for file pieces, putting them together and creating a header file for them so they can be addressed/found/used.

There do exist "secure delete" programs that once you delete a file with that utility, all the pieces of the file are deleted (or overwritten with random data), so there is no way to go back to find it.

Feel free to follow up with any additional questions you might have.

Good luck!

Hard Drive Problems

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I can answer questions about server hardware RAID and general storage for servers and PC's - hard drive issues, troubleshooting, advice, specs, and information. While some apparent drive/RAID array failures can be recovered, I can only provide advice/recommendations in the event of catastrophic data loss. I don't assist in actually recovering from this type of data loss on this forum.

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I worked as an analyst in Dell server support for 2 years, and have since worked with many Dell PowerEdge servers. I am currently employed as IT Manager. I am currently ranked in the top 5 All-Time in Server Hardware and Hard Drives in a very popular and large forum similar to AllExperts.

Education/Credentials
I have a BS in Computer Science and have earned the following certifications: CompTIA Security+, A+, Project+; CIW Web Design, Database Specialist; Microsoft Windows 7; Dell DCSE Server. I am also an expert in Windows 7, Servers, and Hard Drives (I don't normally do XP - not because I don't know it inside and out, but because I have "retired" personal support for XP, and I want to see it die :)).

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