RAID and USB

Quote from Relish7379

I am new to OMV. I think I am correct in thinking that OMV does not allow RAID with USB HDD?

Is there a technical reason for this?

or is it a non technical reason such as no demand?

Is USB regarded as bad for non RAID? or just RAID?

Welcome to the forum.

The main reason why it was decided to remove support for arrays created with USB connected drives is that USB connections are not as stable as would be desirable.

It is common for a disk connected via USB to end up being unmounted at some point inadvertently. On a single data disk it can cause problems in the GUI but all of them can be solved. In the case of an array, this situation can end with data loss. This happened several times and finally that decision was made.

Search the forum and you will find many old threads on this topic.

The issue revolves around bandwidth. For a RAID array to assemble, each drive needs (roughly) equal bandwidth. To achieve that, again in rough terms, SATA and SAS interfaces are capable of providing parallel data stream processing to each of the drives in an array.

USB, by it's very nature, is "serial". One drive is accessed at a time. While USB RAID can work, it's not reliable. As chente has said, there are examples on the forum.

If you're using an SBC (a Raspberry PI or other), there are alternatives to mdadm RAID that are very similar and arguably better.

Quote from johan53

Dear I noticed that with the version 6.x you still had the possibility to go for Raid, but in the 7.x this is no more. Is this so or is this fixable that I can still put my disks in Raid ?

In OMV7 mdadm has been moved to a plugin. You must install openmediavault-md to use Raid.

As for the usability of Raid with USB-connected drives, it remains the same in OMV7 as in OMV6. It can't be done.

Quote from dc3ax

What is that for a decision?

Because raid on usb devices is a terrible idea. Many usb enclosures will put the drive to sleep which can cause the array to not re-assemble (all data lost). Raid is about redundancy and availability and usb is not meant for either.

Quote from dc3ax

In my case I am not using several random drives connected to a bunch of external USB hubs. I am using a RAID case

Those aren't much better if you look at my previous arguments.

Quote from dc3ax

it is also blacklisted?

It is still usb connected drives. OMV and Linux do not know that they aren't just individual USB drives.

I would argue that you don't need raid though but I will leave that alone....

Quote from dc3ax

Sorry, good bye OMV

Calm down... Just create the array from the command line and then you can do everything else from the web interface. The web interface is only stopping you from creating the array.