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According to this article, I need to eject my flash drive before removing the flash drive from the computer. Do I need to do this, and if I do, why?

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Never did it, never lost any files. Had my flash drive for 7 or 8 years now.. – picakhu Jun 17 '11 at 22:04
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personal experience has shown that non ejected drives from windows are rejected by unix. however the major reason this is "required" is to ensure no reads/writes are done to files on the drive as you're removing it and if it is used as temp swap space these swap files are swapped out to the other drives. (no refs so put as a comment) – ratchet freak Jun 17 '11 at 22:08
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For reference, i've personally seen files not appear on a flash drive due to the drive not being "ejected". The risk of data loss is almost entirely dependent on how long ago the last writes occurred (which is heavily influenced by the characteristics of the device and the OS). – cHao Jun 17 '11 at 22:17
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Skeptics? Really? – Adam Davis Jun 17 '11 at 23:33
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I'm closing this as off-topic. I'm not migrating this to Super User because, if I do, Ivo will yell at me. – Borror0 Jun 18 '11 at 3:40
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closed as off topic by user unknown, ChrisW, Patches, Borror0 Jun 18 '11 at 3:40

Questions on Skeptics - Stack Exchange are expected to generally relate to scientific skepticism, within the scope defined in the faq.

2 Answers

up vote 3 down vote accepted

Well, one way to answer the question is to find examples of people who have experienced negative consequences of removing the flash drive without ejecting. If they exist, then there's at least cases where it has produced negative results and can be removed from the "entirely folklore" category. Turns out that there are some:

So, at least three have experienced at least some issues from doing this. For the why, it comes down to removing the drive before a write has finished. If the drive is being accessed and written to, and you yank it, the bits that have been written will be unintelligible the next time. I have a hard time imagining that this would full corrupted the drive itself, and find it more likely that the files might be corrupted/damaged. I say this as it's atypical for a computer to access something crucial to the drive, such as the Master Boot Record which tells the computer where the partitions are (in essence, where it can store the data) and what the partition type is (aka the "format" -- NTFS, HFS+, EXT, FAT, etc.). Typically this requires some intent.

Despite my intuitions and working knowledge of hardware, in answer to the question, "What would happen if I remove my USB flash drive while data is being written to it?", Integral Memory, a manufacturer or memory storage devices, says:

Your data on the USB Flash Drive can become corrupted or lost and the file system of the Flash Drive may become corrupted as well. It is always recommended to use the "Safely Remove Hardware/USB" option when using your Integral Flash Drive on a PC or Mac. (SOURCE).

So, apparently the file system may actually become corrupt. I would not have suspected this. Based on this information, I would say that those who have not had an issue with pulling the drive waited long enough for any writing to finish. Those who have experienced issues may have been subject to some hidden processes accessing the disk of which they were unaware.

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the filesystem becoming corrupted would be because when adding/removing/moving a file to/from/on the drive the OS has to alter the file access table (or whatever format is used) and when that becomes corrupt you'll need special tools to rebuild it (possible to do it by inspecting the entire drive and finding which blocks belong to which files and which are empty/corrupt but not all OSes would come with the tools build in to do so properly) – ratchet freak Jun 18 '11 at 0:45
@ratchet: huh. Cool. Does that have anything to do with metadata storage, or is that something else? – Hendy Jun 18 '11 at 2:23
just the file table normally (or more precisely the directory structure) but that is all implementation dependent on when those changes are written to the drive (some OSes might cache the (changed) file table in RAM after copying a large directory to it but not write it out yet in case the user does another large change which would result in the date being written out but it is unreachable using the old file table which is still there on the drive) – ratchet freak Jun 18 '11 at 2:49
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up vote -2 down vote

Your source is lousy. It gives incomplete information:

Close all files you accessed from the flash drive.

That's not necessary. If you opened them just for reading, there is no problem, or if you save them elsewhere.

This is necessary for the device to be removed properly. If you haven't closed them yet, do so, but don't forget to save them.

Well - why should you save files you only read? MP3s, PDFs and so on?

Go to the notification area in your task bar. It should be located on the bottom right side.

No. Maybe on Windows, and maybe in former times.

You will see a USB icon with a check on it. Use your mouse to right-click the icon. Click the Safely Remove Hardware command using your left mouse button.

That's just usable if you use Windows. Maybe you do.

Since flashdrives can't be written as often as harddrives, they often have an delayed write operation, and only write every x minutes. So if you perform a write operation, it might still be pending. Calling 'eject' on linux, or 'save remove' will perform the writing so no data is lost.

But imho more a servicequestion for Superuser, not a sceptics question. I vote to close.

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