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I've been using a HPE MicroServer Gen10 for a while, and I'm about to setup a RAID 1 configuration for my OwnCloud storage. The server is running Ubuntu 17.10.

The disks are simply two Western Digital RED 1TB 64MB.

From what I've read, hardware RAID using the Marvell controller isn't really an optimal choice, since the support is limited (please correct me if I'm wrong) - and it could also cause me trouble if the controller itself breaks down.

Then I found MDADM which seems great. However, I haven't been able to find a clear answer to my one, simple question:

If one of my disks breaks down, can I just keep reading data from the other one, - removed, or not removed - from the software RAID array?

And can I just remove the working disk from the server and simply plug it in like any other disk in another system, and read from it?

Bonus: Does MDADM itselfs detects faulty disks and reports it to the user?

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Yes,you can.

If 1 disk breaks down, the RAID device will remain visible (albeit degraded). If it's not working, pulling the bad disk out will fix it issues.

It is also possible to read the contents from the MD partiotion by directly mounting it and specifying, if necessary, the filesystem type (or activating lvm). Normally the metadata is at the end of the disk, so it just works.

Bonus - If you edit (from memory) /etc/mdadm.conf you can add an appropriate email and get a notice when the array degrades. You can also cat /proc/mdstat to see the current status.

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  • This is exactly what I wanted to know. Thank you very much for a short and clean answer.
    – swaglord mcmuffin'
    Commented Jan 24, 2018 at 11:46
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    metadata has defaulted to going at the start of the disk for quite a few years now, so you have to activate it through mdadm and can not access it "normally" without mdadm. You need to force mdadm to use metadata format 0.9 or 1.0 for it to go at the end.
    – psusi
    Commented Jan 24, 2018 at 19:33

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