virtualbox.org

I'm having great problems seeing a partition on a portable HD attached to Windows XP as a guest on OS X 10.7.4 using virtualbox 4.1.18.

The HD is a Toshiba 2.5 steel SATA 500GB disk, partitioned into 450GB and 50GB - the smaller partition has always been used for encrypted secure files and has always been visible in both Virtualbox Windows and Mac (when interrogated).

I used to be able to see the large partition in Explorer when it was my backup for a Windows based system, but once I changed it to the Mac it hasn't showed. I've tried reformatting on a Windows XP machine but this hasn't worked.

Any clues please?

retured user

Your problem is reading the large partition (from a portable drive) on your Mac host? That doesn't sound like its a VirtualBox question, but the quick answer would be that the filesystem has to be one which a Mac recognizes by default - so question one is, what filesystems are used by the two partitions on the drive?

I'm not a Mac user hence not sure about any of this, but basically: if the partition uses FAT format that I would expect a Mac to see it ok. If the filesysten is NTFS then a Mac may not like it right off, you may need to install an NTFS driver (if available).

A Mac should see the partitions even if it doesn't understand the filesystems used.

Thanks mpack for the response - you suggest reasons for another problem (reading Mac backup on Windows).

But my problem is that I do not see my NTFS (or exFAT) formatted partition on Windows XP in VirtualBox running on a Mac although the other partition on the portable HS is visible. Devices, USB devices show the Tosh is connected, as does Add hardware in Windows, and of course I still see the other partition that I haven't done anything to. When Virtualbox is closed, I do see the partition, although as read only.

On first setting up Windows XP in Virtualbox I was able to both read and write to the partition. However since reformatting the partition for a Mac back-up, noting I couldn't see the files in any Windows XP environment so deciding to switch back to FAT/NTFS as secondary back-up to achieve portability, I haven't been able to see that partition in Virtualbox Windows XP so can't use it.

Virtual machines don't see physical host partitions, and I don't support people attempting to use raw partition access (the latter is an dangerous expert level feature: those qualified to use it don't need support).

Thanks mpack for the response - not sure where you get that I have done a raw partition whatever that is.

Rephrasing my problem. In pre-Mac days (using Windows XP)I split the Toshiba HD into two partitions. On going to the Mac and installing virtualbox to continue to run Windows XO, I was able to see and use both partitions. I used the Mac disk utility 'erase' function to, I believe, reformat one partition. On realising that this Mac formatted partition could not be seen in a Windows environment I have converted the partition back to NTFS to achieve portability in my back-up or copy of data. However the reformatted partition is not seen in virtualbox, although the other partition is still visible. The NTFS partition is however visible, read only, in Mac.

I classify myself as an experienced, but not a technical, user.

Within Windows XP, does the device manager know of the partition?
If so, then XP is not recognising the partition as being NTFS formated.
Frequently, I have had to reformat from within XP.
To be 'safe', I have OS X format the partition as FAT so that XP will recognise it,
then have XP reformat as NTFS once I have verified that this is the desired partition.

Thanks ChipMcK for the input.

Within the guest Windows Device Driver recognises the device but not the partitions.

I have tried reformatting both within the guest Windows os and on two other Windows machines as sole operating systems but continue to get that the guest Windows recognises the drive, recognises the other smaller partition (that hasn't been reformatted at any time) but will not recognise the 'main' partition.

What partitioning scheme was used on the disk?
XP predates MS support of GPT (they included partial support in Vista).
And MBR limits the disk to 4 (four) partitions.
Window 7 supported GPT, with some support of EFI initially.

Thanks ChipMcK,

Don't know what scheme was used. The HD was initially partitioned on my old Dell with Windows XP; and both partitions were recognised when I switched to Mac and then added virtual box. It is only since reformatting through the Mac and then to achieve some portability reformatting back to NFTS or FAT that the partition is not recognised - almost as if the Mac has stopped any ability to go back to a Windows environment.

Resolved, thankfully. And stupidly simple.

My unrecognised partition had the same drive letter as a shared folder created in virtualbox - I hadn't recalled, or even realised, that drive letters are hard coded into the partition and when I picked up the new shared folder of course the external drive was not connected.

Thanks for the contributions.