Reading single disk volume (JBOD) on a computer

[NumberFour]

Hi everybody,

I searched over network but didn't find a clear answer to my question.

I would like to configure my NAS with a first RAID volume (let's say volume A) with 3 disks, to prevent from disk failures, and a second volume, with only one disk, to automatically backup critical data from volume A (using backup jobs) on it.

A single disk volume is automatically configured as JBOD on the ReadyNAS. In my mind, because it's a single disk, I shall be able to read it on a computer, on linux, or on windows using a software to access ext4 partitions. I know that it's hard with multiple disk volumes (RAID 0 or more), but is it possible with a single disk volume in JBOD ?

The purpose is to prevent from any ReadyNAS failure (the hardware) with my important data !

I didn't find any clear answer on the web, hope someone can answer and maybe give more information about that, for reading this disk on linux and windows (which software to use to read ext4 on windows 0)

Thank you in advance for your contribution !

[StephenB · Accepted solution]

It looks like your enclosure can't handle disks > 2 TB.

You might need to get a USB 3 enclosure or SATA->USB adapter.

[StephenB]

The volume would be btrfs, not ext4.

There is a related thread here: https://community.netgear.com/t5/ReadyNAS-in-Business/OS6-Data-Recovery-How-to-Mount-BTRFS-Volumes/m...

Though that thread is quite old, and you probably don't need to assemble the volume with jbod.

It's clear that this can be done, but if it is an essential part of your data recovery plan you should check your ability to read the volume (as the poster on the old thread did).

[NumberFour]

Hi again,

Thanks for the answer.

I tried, but I don't manage to mount the volume...

As I am using a laptop, I don't have sata directly accessible, that's why I'm using an external hard drive box, which is correctly detected as USB to SATA bridge

When I connect it, this is what appears (fdisk -l) :

Disque /dev/sdb : 746,5 GiB, 801569726464 octets, 1565565872 secteurs
Unités : sectors of 1 * 512 = 512 octets
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0x00000000

Périphérique Amorçage Start        Fin   Secteurs Size Id Type
/dev/sdb1                 1 4294967295 4294967295   2T ee GPT

It's a 3TB HDD, so I'm surprised not seeing anywhere the size, maybe due to JBOD format ?

And then, here are the results of the different commands I tried :

sudo mount -t btrfs -o ro /dev/sdb1 /mnt

>mount: special device /dev/sdb1 does not exist

sudo mount -t btrfs -o ro /dev/sdb /mnt

>mount: wrong fs type, bad option, bad superblock on /dev/sdb,
       missing codepage or helper program, or other error

       In some cases useful info is found in syslog - try
       dmesg | tail or so.

sudo mdadm --examine /dev/sdb --scan
sudo mdadm --examine /dev/sdb1 --scan

(There is no output for boty of those commands)

sudo btrfs device scan /dev/sdb
>Scanning for Btrfs filesystems in '/dev/sdb'
>ERROR: device scan failed '/dev/sdb' - Invalid argument
sudo btrfs device scan /dev/sdb1
>ERROR: not a block device: /dev/sdb1

I'm not a linux expert (far from that) and I don't find enough information of how to do it on Internet.

Maybe someone has an idea of what has to be done, or of what I'm doing wrong ?

Thanks in advance for all help !

[StephenB · Accepted solution]

It looks like your enclosure can't handle disks > 2 TB.

You might need to get a USB 3 enclosure or SATA->USB adapter.