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Answer ID 23   |    Updated 05/27/2016 09:37 AM

Operating Systems' Volume Sizes

Windows 7/8, Vista, Server 2003/2008 and Mac OS X operating systems support volumes larger than 2TB. Windows XP supports only a partition size of 2TB.

File System Format	Compatible With	Max Volume Size
HFS+	Mac OS X DroboShare	16TB
NTFS	Windows 7/8, Vista, Server 2003/2008, and DroboShare	16TB
NTFS (XP Compatible)	All Windows and DroboShare	2TB
FAT32*	All Windows, Mac OS X, and DroboShare	2TB
EXT3	DroboShare, Linux	8TB**

^* FAT32 is an older file system format that is generally less protective of your data than modern (journaled) file systems. It also delivers slower performance and imposes file-size limitations. Because of these drawbacks, Drobo does not recommend using the FAT32 file system option unless absolutely essential

^** EXT3 is supported only for volume sizes of 1TB or 2TB on 1^st and 2^nd generation Drobos. However, customers have found that they are able to have volume sizes (LUNs) greater than 2TB by attending to two items:

• Ensuring the Linux kernel is 2.6.24 or greater
• Enabling the selection "Enable Block Layer-->Support for Large Block Devices"

See How do I format my drives in the EXT3 file system format so my Drobo storage device works when hooked up to a Linux machine? for further information on formatting volumes in Linux.

If Disk Space Exceeds Volume Size

If the amount of available protected storage^*** in your Drobo storage device ever exceeds the size of the volume that you picked originally during installation (when you add one or more additional disk drives), then the Drobo device will automatically create a new volume of the same size as the original volume on 1^st and 2^nd generation Drobos. Your Drobo handles this situation automatically. When the total storage offered by the inserted drives exceeds your volume size, Drobo Dashboard will automatically create a second volume (of the same size) which appears as another volume icon on the Mac's Desktop or as a new drive letter or partition on the PC. You will be asked to format and name the new volume. Formatting the second volume/partition will not affect the first.

If you are using Drobo S, DroboPro or DroboElite, you will be prompted by Drobo Dashboard to create another volume through the Volume Management facility.

^*** This is the same as the "Available for data" section shown by the Drobolator and on the Drobo Dashboard under "How is my storage being used?"

Maintaining a Single Volume

If you want to maintain all data on a single volume rather than on multiple volumes, you’ll need to migrate the data onto another Drobo or storage device, reformat the original Drobo device to the volume size of your choice, and then move the data back. Many customers choose the largest capacity available during initial setup to avoid having to move such large amounts of data around.

Thin Provisioning

You can format your Drobo device's volume size as 1TB, 2TB, 4TB, 8TB or 16TB (even without having that much disk space). This ability to format your volume to be larger than available disk space is called “thin provisioning.” It allows you to grow into a single, large volume over time rather than needing multiple smaller volumes. However, keep in mind some operating systems have a 2TB per-volume limit (as detailed in the chart above).

Note: Even though your operating system may prompt you to format your volume, it is better to use Drobo Dashboard for formatting. Drobo Dashboard allows you to format your volume to a size larger than the available disk space (thin provisioning).

For related information, see: 

• What is my real storage capacity when installing disks of different sizes?
• Why is there a difference between available storage as reported by the operating system and by Drobo Dashboard?
• Why is my usable capacity lower than I expected?
• Why don’t I see any increase in storage space after adding a larger disk drive?
• How many LUNs Can I Create on a DroboElite/B800i?

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