Given that the Drobo, when connected via USB, is detected as a mass storage device, can I not simply format it to any file system I like? I’m wondering where these restrictions to NTFS, HFS+, FAT32 and ext3 come from…
I’ve looked at the Linux dashboard software to see how that formats it; it simply calls “mke2fs”.
So, in theory, can I not simply plug it in and format it (via the command line) to ext3 with a block size of 4 KiB and get past the 2 TiB volume limit? Or indeed format it to any other file system I choose? Are the four file systems given on the Drobo site not restrictions at all, merely a list of the only ones the supplied software can support?
Drobo uses “Thin Provisioning”. This means that Drobo only allocates space on the physical disks when you actually write files to it. It then releases the space when you delete files.
This allows you to format it to a set size (e.g. 2TB or 16TB) while not having that much actual space on your hard disks. You can then add or replace hard disks later as needed without having to reformat.
In order for this to work Drobo needs to understand how you have formatted the drive - this is why it only supports a selection of filesystems.
For Linux the support is in ‘beta’ - so it has been implemented on the Drobo but its not officially supported by Data Robotics if you have issues.
This beta support lists compatibility up to 2TB.
You can format an ext3 volume larger than 2TB if you have a very recent linux kernel. However a google search on this reveals that people do have issues with it. Specifically when using larger than 2TB ext3 volumes space may not be freed up when you delete files.