Dual Disk Redundancy

Got my Drobo S a few days ago and am confused about Dual Disk Redundancy space usage.

I have the following drives:

I did a reset of the drive. Then went into tools and checked the DDR option. I then created a volume. It showed that there is 1.13tb of available space, and I went with the default volume size of 2tb, using XP-mode NTFS. When I format the drive (using Drobo Dashboard, not Windows), I end up with two volumes. Why is it doing that? I would expect there to only be 1 volume with 1.13gb of free space.


It should create only 1 volume. 1.13 TB of available space can only give you 1 2TB volume.

Can you reset it from the dashboard and reformat?

I’ve done that twice. Each time, I end up with two volumes mapped to two drives on my Vista box.

Wow, that is so odd. Can you please create a support case?

Include screen shots of opening screen of dashboard, data tab, tools tab, disk management showing the 2 volumes.

I already have a support case open (Incident: 091217-000029). I was posting here in hopes that someone had seen this and had an answer. After spending the weekend playing around with the Drobo, I figured out a workaround to the firmware bug. Here is the note I just added to the case:

Thank you for contacting Drobo Technical Support. To get back to one volume you need to move all data off the DroboS to a safe location.
Reformat the all volumes on the DroboS. This will take you back to one volume with the Dual Disk Redundancy turned on.
After playing around with the Drobo over the weekend, I have discovered a bug in the firmware. Even if you check Dual Disk Redundancy, when you format as XP-compatible NTFS and the original volume is over 2tb, it will create two volumes, even though with DDR on, the new volume will be well under 2tb. This only happens in XP-compatible NTFS mode. If using the Vista-style NTFS, it will create everything in one volume.

I did discover a way to make the Drobo keep everything on one volume when using XP-compatible NTFS mode.  I have 5 disks in the Drobo (see the list below).  I removed the last two (the 2 1tb WD drives), and reset the Drobo.  I then first checked the Dual Disk Redundancy option and let it finish before formatting the drives in XP-compatible NTFS.  Once the DDR and formatting were complete, I then added one of the 1tb drives in slot 4.  Once the drive was recognized, formatted and the total space pie-chart was updated, I then added the 5th drive (another 1tb drive).  Now everything looks good and there is no second volume.

This is a bug.  If you have more than 2tb of drives, but check the DDR option before formatting as XP-compatible NTFS, and the resulting volume will be less than 2tb, the software should not create more than one volume.

Please answer the following questions:

  1. How many drives do you have in your DroboS, who are the manufacturers and what size are they?
    Slot 1: Seagate Barracuda 7200.10 750gb
    Slot 2: Western Digital WD Caviar SE16 250gb
    Slot 3: Samsung SP2504C 250gb
    Slot 4: Western Digital Caviar Black WD1001FALS 1tb
    Slot 5: Western Digital Caviar Black WD1001FALS 1tb

  2. Open your Drobo Dashboard - Advanced Controls - Tools and tell me what it says under “Installed Versions” in the bottom right-hand corner of the window?
    Drobo Dashboard =1.6.6 [1.6.24917
    DroboS Firmware =2.0.0 [5.11.24786

  3. Did you setup and format your DroboS through Drobo Dashboard or Disk Utility Disk Management
    I used Drobo Dashboard

  4. Please follow this procedure to run a Diagnostic on your Drobo. Please attach the diagnostic to your reply to this email.

  5. Right-click on the Drobo Dashboard icon running in your computer’s system tray, in the bottom right-hand corner of your screen, next to your clock.

  6. Select “Get Diagnostic Information.”

  7. Attach the file in the Reply to this e-mail.
    Output attached.

Also, I am still unable to get the Spindown parameter to remember the setting.  No matter what I change it to, it keeps going back to "never".  What is preventing the Drobo from keeping the setting I want?