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I've been considering buying a Drobo (not Pro) to use for an external storage and backup device. For my application, it is important that I can use Truecrypt to encrypt the external device.

Since the Drobo manages the usable space inside of the Drobo device itself and passes an unchanging 16 TB device (by default) to the OS, is it still possible to use Truecrypt's "Encrypt a non-system drive" option with the Drobo and use Truecrypt to mount it as you normally would with a conventional external hard drive encrypted by the same method?

I've searched for information on this for a while and didn't find anything useful. Thanks for the help!

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Is there any reason why you have to encrypt the entire disk and not create a volume file? – Crash893 Nov 5 '09 at 20:47
up vote 4 down vote accepted

Yes, you can use TrueCrypt on a Drobo volume. To the OS (and TrueCrypt), it's just another disc drive. The device takes care of the spanning the volume across the discs and the data protection.

However, you're not going to see 16 TB, even with a Drobo Pro (at least not until they start making drives with capacities above 2 TB). They say a standard Drobo will give you about the sum of the capacity of all the drive minus the capacity of the largest drive (it can survive the failure of one drive). So, if you filled a standard Drobo with 2TB drives, you'd have about 4 bays * 2 - 2 = 6 TB of storage space. A Drobo Pro is the sum of the capacities minus the capacity of the two largest drives (it can survive the failure of two drives). So, if you filled a Pro with 2 TB drives, you'd have about 8 bays * 2 - 2 - 2 = 12 TB of storage space.

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Let's say I encrypt the entire drive with TrueCrypt. How does the Drobo handle it when I add a new HD? I'm thinking the Drobo wouldn't be intelligent enough to extend the encryption across the new available space so that space wouldn't end up as part of the encryption but as new, unallocated space. Is this incorrect? – roknir Oct 23 '09 at 1:39
@roknir: The Drobo takes no part in encrypting the data that resides upon it, TrueCrypt does. In fact, the Drobo knows nothing about the data that resides upon it. The Drobo's only responsibility is to make sure that there is always X amount of storage space, even if one of the drive fails. When one drive fails, the OS (and TrueCrypt) don't even know it. When you put in a replacement drive, the Drobo takes care of rebuilding redundancy. Perhaps you don't quite understand RAID? I'm no expert either, have a look at this: – raven Oct 23 '09 at 2:44
I recently picked up a Drobo and loaded two 1.5 TB drives into it. I had TrueCrypt start to encrypt the entire Drobo device (did not create any partitions or volumes first) because this is usually easier to work with on externals in Windows. TrueCrypt made it to just under 67% encrypted and is moving along very slowly. The Drobo sees itself as 100% full and wants me to add an additional disk. Drobo Dashboard shows roughly 50% in used space and 50% in unallocated space. It looks like I must create a volume on the Drobo and then encrypt the volume rather than encrypting the device itself. – roknir Oct 23 '09 at 22:10
Ah, this confirms it: You can't fully encrypt the Drobo by encrypting the full device or a whole partition. The only option is to use a fixed-size file container. – roknir Oct 23 '09 at 23:15

When you want to encrypt an drobo volume with truecrypt, be shure you encrpt a fresh drobo volume and use the truecrpyt option "Quick Format" (its a checkbox right in dialog of filesystem options). With quick format, true crypt don't formats all blocks and the drobo isn't moving very slowly.

Checklist: for use with >2TB volume on windows vista or 7

  1. Create a new drobo volume via drobo dashboard, i.e. 4TB
  2. Go to Windows-SystemManager and initialize the new volume as GPT (its registered as new drive, otherwise every time opening drive manager you get warned about uninitialized drives)
  3. open TrueCrypt Create Volume
    1. Select "Encrypt a non-system partition/drive"
    2. Volume Type: Standard TrueCrypt volume
    3. Volume Location: new Harddisk, i.e. Harddisk 6, be shure not selecting the 128MB partition1 on drive. After select "\Device\Harddisk6\Partition0" must be located.
    4. Volume Creation Mode: Create encrypted volume and format it
    5. Encryption Options: select your favorite
    6. Volume Size: cannot be changed, this sample uses 4096GB
    7. Volume Password: your choise
    8. Large Files: Yes, if you want to store files bigger than 2GB
    9. Volume Format: NTFS, Cluster: Default, Check the Quick Format option!!!
    10. Press the Format button.
  4. Finished, mount the new encrypted drobo volume using TrueCrypt

The DroboDashboard Volume Manager shows only the registered volumes, but not their file system and used space. The pie chart displays the correct usage of space. Be warned: when you delete files inside the encrypted volume, the drobo gets no information about deletion, the space seems to be in use. Its the same with a fully inflated tc file container, deleting files doesn't free space on host drive.

Use this description at your risk.

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I suppose then, a lot depends on whether the OS prefers to overwrite deleted files before writing to never-written parts of the "disk". If not, frequent writes & deletes could fill up the Drobo even though there's really nothing being stored. – Brian White Sep 10 '12 at 3:29

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