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I bought a Fujitsu Celvin Drive D100 (external USB HDD) as new and now I want to partition and format it for Linux use. I noticed however that at the factory they have left some empty space before (1 MiB) and after (2 MiB) the single NTFS partition. I called the Fujitsu helpdesk and they didn't seem to know why the unformatted space is there but – of course – recommended that I leave things as they are. Could there be something crucial hidden there or are the empty areas there for (data) safety reasons? Can I use the entire disk without problems? Please don't question my reasons for wanting 3 extra megabytes on a 2 terabyte HDD, I only want some information. ;-)

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I doubt that space is anything hidden or anything for safety. I always use the full disk space without any problems. My guess is that space is related to block size in the particular type of format (ntfs, ext3, etc.) – viking Jul 1 '11 at 20:02
You can always try giving them a letter temporarily in disk manger ans see if there is something interesting there. – KCotreau Jul 1 '11 at 21:52
@KCotreau, that likely won’t work because they’re probably unallocated. He would have to allocate them as some partition type (and probably format) before being able to assign them letters. To see what’s there without altering it, you’d need a low-level disk editor like Norton Disk Doctor in DOS or in Windows, Runtime’s DiskExplorer or HxD (Extras->Open Disk) – Synetech Jul 2 '11 at 6:33
@Synetech inc. You are correct if it is unallocated, but it is a way to check if there it is a hidden partition with actual data on it if it is a real partition. He only really cares if it is allocated, so no disk editor is necessary. – KCotreau Jul 2 '11 at 12:01
It sounds to me more that he wants to know what’s in it (ie, is it important), not just if it’s allocated. I would recommend using a tool to dump the partition tables to a text file and keep that somewhere, then wipe and partition as desired. That way, the original layout is saved and can be restored if necessary. – Synetech Jul 2 '11 at 18:08
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3 Answers

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My first guess would be that they are some kind of reserved partitions for the external enclosure, but you said Fujitsu didn't know why they were there. I would leave them alone just for warranty purposes and to make sure it keeps working with the enclosure. It's only 3MB.

If you plan on taking the HDD out of the enclosure in the future, then remove them at that time.

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I would expect that the first 1MB that is unallocated is because modern partition managers take account of the fact that they may be creating a partition on either a drive with 4kb sectors or an SSD and so the partition manager (for simplicities sake) will use a "one size fits all" approach rather than working out all the possible variations that will work for each type of drive.

Both the 4kb Advanced Format drives and SSDs require the partitions to be aligned to the cluster (or SSD erase cell) for optimum performance and the 1MB gap at the start of the disk is a nice common figure that will work for both types.

Heck on a several hundred gigabyte drive 1MB is nothing to worry about.

As to the 2MB at the end of the drive, chances are that whatever partition manager was used simply rounded up or down some particular number and ended up with a small bit of space left over at the end of the disk when it created the partition. I've seen it happen quite often on various drives and from various operating systems partition managers.

In the long run you probably shouldn't care as 3MB is an absolute tiny amount of space compared to modern many-hundred-gigabyte drives and reclaiming it is not really going to mean you can store that much more data, maybe 1 mp3 or a some documents.

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That’s a an interesting theory, but I would think that a partition manager that is advanced and modern enough to be aware of SSDs with 4KB sectors would be able to detect what the disk actually is and handle it appropriately. Plus, if your theory is correct, then I would expect that every single partition would get a buffer like that. Also, even old partition managers were able to use whatever space was left as opposed to just rounding (unless there was enough space, then they would force your to “snap” the partition size to some, bizarre, interval—which I still don’t understand). – Synetech Jul 2 '11 at 18:11
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You may think that, but Mokubai is right nonetheless. And you've not read the question carefully and noted that there is only the one partition on the disc, so you don't know that the "buffer" would not be "after every single partition" and cannot justifiably state that it isn't and then base a further conclusion upon that. Read and learn what Rod Smith has to say on this entire subject. – JdeBP Jul 4 '11 at 12:20
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up vote 0 down vote

I'm the same person as the original poster; I just created an account so I can't select the best answer and whatnot.

I did something like Synetech inc. suggested. The beginning of the drive contains a boot sector of some kind and then this hexa string over and over again: e8 97 d1 c3. The end of the drive is just zeros. I read JdeBP's link and it now seems that the extra space is there just because some Windows partitioning tool likes to do it that way (to make the drive efficient). I think I can use the whole hard drive (leaving space for a boot loader) without problems as no-one reported them. I can't imagine this drive uses Advanced Format but better play it safe by using 8-sector limits.

This is how I made a back-up of the drive:

# dd if=/dev/sdb of=beginning.img bs=512 count=2048
# dd if=/dev/sdb of=end.img bs=512 skip=3907024896
# ntfsclone -s -o backup.ntfs /dev/sdb1

Then I put everything in a compressed archive file. I can restore the drive to its current state should a warranty issue arise. Thanks for everyone's input.

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From the GRUB 2 documentation: "on modern disks, it is often a performance advantage to align partitions on larger boundaries anyway, so the first partition might start 1 MiB from the start of the disk." – Roger Olsson Jul 7 '11 at 0:05
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