EXT3 Linux, Drobo (2nd Gen) Cannot reclaim space - blue capacity Lights do not go out


My wife bought a new Drobo 5D and gave me her old Drobo 2nd Gen. This post is entirely about the Drobo 2nd Gen.

Q1: Does anybody know if the DROBO 2nd Gen will effectively reclaim space when an EXT3 filesystem is used? I have been trying this for days (always 2TiB LUN size as recommended) and cannot get Blue Lights to turn off no matter how much data I delete and seemingly no matter how I do it (including a re-format).

Q2: For ext3 DRI recommends a kernel version 2.6.31 or greater. For reasons explained below I am stuck on version 2.6.17. The kernel recommendations seem directed mostly at Firewire users and people wanting LUN sizes greater than 2TiB. Does anyone know concretely (preferably not speculatively) whether the issue I’m having is directly related to the kernel version being too low?

Full Story:
I have a ReadyNAS NV+ that is at full capacity and I thought I could throw a couple of drives into the 2nd Gen Drobo and connect it to the ReadyNAS via USB 2.0 to increase capacity. I bought two (2) x 3TB WD RED drives and put them in the Drobo 2nd Gen.

I used a mac version of Drobo Dashboard to set the LUN size at 2TiB, as per recommendations all over the place. I then formatted the partitions using the mkfs.ext3 tool.

In my initial data copy, I accidentally filled one LUN (ah, hard links) and the DROBO began asking for another drive. But I deleted ALL the data and the blue lights never turned off and the drobo continued ask for another drive. I FORMATTED the LUN in question, and the drobo lights STILL stayed on and the drobo still asked for another drive.

So, I reset the drobo.

This time I again set the LUN size to 2TiB and I used drobo-utils to do the partitioning and formatting to EXT3. I copied 500GB of data to the Drobo and two blue lights turned on. I deleted the data, the blue lights stayed on. I copied 500GB again to the Drobo, a third light turned on. I connected the drobo to a modern computer with a linux kernel version 3.13 and ran an fsck -f. Then I deleted the files. Then I ran fsck -f again, then I rebooted the drobo.

There is ZERO data on the drobo now and 3 blue lights are STILL on.

What to do?

Edited: Sorry, I forgot to explain why the ReadyNAS kernel is not easy to update from 2.6.17. The ReadyNAS is a legacy product with SPARC architecture and I do not have the knowledge (nor found it anywhere on the internet) to compile the kernel with all the non-standard modules and drivers required.

As a note, today I changed one of the partition types from GPT to MBR and reformatted in the process…and to my surprise the Drobo began to churn through the data and slowly over the course of an hour or more, one by one the blue lights went off. Drobo-utils reported 1% disk use, down from 31%.

So, today I connected the Drobo to a Raspberry Pi, and dumped about 80GB of data onto it, enough for drobo-utils to show 2% data use. Then I deleted the files and yes, after a couple dozen minutes, with intermittent drive activity, the drobo reported 1% data use. I find this encouraging.

So, I’m wondering now if there’s any difference between GPT and MBR partition support in the Drobo with these lower kernel versions?

Today I am copying a couple hundred GB from the ReadyNAS to the Drobo via USB (enough to make at least one blue light come on), and then I will delete it to see if this time it’s working. I will report back.

Did you find any solution to this?