Drobo 5N; Drobo 5D: 64TB Volume Support


Article Id: AA-01867 Last updated date: 04-20-2017

Drobo 5N:

With firmware revision 3.5.2, the Drobo 5N now supports 64TB volumes for newly created packs. Unfortunately packs created before 3.5.2 cannot have their volume size upgraded. 

The 5N runs on a 32-bit ARM processor, and uses the Linux ext4 filing system. The maximum volume size that ext4 can support is based on the number of pages the processor can address.  On a 32-bit ARM processor, that ends up being a 2^32 4K pages, which is 16TiB of addressable storage. To go beyond this requires either a 64-bit processor, or a larger page size.

The new 3.5.2 firmware has a special hybrid page size of 16KB, allowing us to increase the maximum volume size to 64TiB. 

However, increasing the volume size also required us to enable 64 bit support in the ext4 filing system. 

Although ext4 does support growing filing systems generally, it is not possible to grow a filing system from a 32-bit version to a 64-bit version. 

As a result, at this time it is necessary to copy data off the Drobo, recreate the diskpack (i.e. reset the Drobo and drives from Dashboard), and copy data back in order to migrate from a 16TB to 64TB volume. 

Drobo 5D:

With firmware revision 3.5.0, the Drobo 5D now supports 64TB volumes for newly created packs. Unfortunately packs created before 3.5.0 cannot have their volume size upgraded. As a result it will be necessary to copy the data off the Drobo, recreate the diskpack (i.e. reset the Drobo and drives from Dashboard), and copy the data back in order to migrate from a 16TB to 64TB volume.