PR4100 - Where is the RAID configuration stored (HDDs or Firmware)


#1

The PR4100 came with 4 Hard drives, 8TB each when I first purchased it. I had configured the old set as RAID 10.
Now they are full.

My question is, whether I can remove ALL the 4 original HDDs that the PR4100 came with, and then add ANOTHER fresh set of 4 hard drives (4x 8TB) and then start to use the fresh set of hard drives as JBOD?

I would like to be able to remove the NEW set of the 4 drives and then replace the OLD set of 4 drives in the PR 4100 whenever I need to access stuff on the OLD set of the drives.

On a normal PC this is possible, since the OS configuration etc is stored on the hard drives. So I can install for example, WIndows 7 on a hard drive, boot with it and use as needed. I can install Windows 10 on another hard drive, remove the drive with the Windows 7 on it and then boot with the Win 10 HDD, without worrying about any config changes or interference between the Win 7 and Win 10.

Is it the same with the PR 4100 also?
My concern is, is the RAID configuration and the other details stored on the hard drives (as would be the case in a computer) OR would the config be stored in the firmware or something?

My ultimate aim is to be able to use different SETS of hard drives on that SAME PR4100 machine as needed without needing to change the settings everytime, just as would be possible in a computer where I can swap and replace the HDDs as needed.

Thank you for your answers.


#2

Yes you can do this.
The PR4100 is able to restore a RAID array, e.g. when upgrading an EX4100 to a PR4100. However it is recommended to number the disks to ensure they are in the same slot.

You can even import the array in another machine or in the PR4100 with different firmware (e.g. debian with openmediavault) with this command:

mdadm --assemble --scan

This will scan the partitions of the disks and normally detect that the first partition is a RAID1 array (with some config backups) and the second partition of each disk belongs to your RAID10 array.
See also

mdadm --examine /dev/sda2

#3

Thank you for the reply but sorry, you did not answer my question. To reword it:

Is it possible for me to remove one SET (ie ALL the four disks) from the unit and then replace them with another set of 4 HDDs and then once again later, replace the OLD set back in whenever I need data from the old set?

Of course, we change the entire SET of the 4 drives everytime.

I want to know if anyone actually has done this succesfully without needing to re-configure the unit at every change.

In other words, can I use the PR4100 unit as an external storage medium and swap various SETS of 4 disks as needed, without reconfiguration? This would only be possible if the RAID details are stored on the hard drives and not somewhere on the controller.

That is why I am specifically asking that anyone who actually had tried it on this unit to please let me know if they were successful.


#4

Yes, as I said, you can import a set of disks straight from the web UI, which is exactly what you want to do: restore array A after using disk set B.
RAID info is stored on the disks. The controller will see an unexpected array of disks but provide an option in the web UI to import the array.
Note that you should swap the disks when the unit is powered off.


#5

Thank you @Tfl . I really appreciate your time. I will give your method a quick try tonight and let you know how it worked out :slight_smile:

Was a little worried initially since I see a lot of “speculative answers” from individuals who did not even seem to have owned the units.

From my experience I know that the data is sometimes stoerd right on the controllers, especially in the Enterprise versions. That was why I needed to be sure.

The 32TB of data on the drives took days to copy to and I do not want to lose it all and start over :smiley:

Thank you very much again for your answer. :+1: