How to mount a software RAID 5 array on FreeNAS?

Question

RAID

There is a file server on FreeNAS 7 installed on CF and a 4x2TB disk in RAID 5. Yesterday CF with the system “died”, and the file with the settings was lost (

How to mount an array on the same system installed from scratch?

Answer 1

If the raid has superblocks, then mdadm --assemble --scan should suffice.
You can restore mdadm.conf using mdadm --examine --scan.
If the metadata was not written, then mdadm --build /dev/mdX -n4 -l5 /dev/sd[abcd]1 or whatever you have.
It can be meaningful to collect with --assume-clean - otherwise the array will try to resynchronize, which is not always desirable. Also, until you make sure that everything works, you should not write anything on it.
It is IMPORTANT to note that it makes sense to do mdadm --examine --scan first to find out if there is metadata on the disks. AFTER that, decide whether to --assemble or --build. And yes, --build is generally not data safe. So be careful.

Answer 2

graid5 dump /dev/ad4 gave the following: similar information is given by ad6, ad8 and ad10 with a slight difference in numbers.
Magic string: GEOM::RAID5
Metadata version: 2
Device name: RAID
Device ID: 2555397599
Disk number: 1
Total number of disks: 4
Provider Size: 2000397852160
Verified: 0
State: 3
Stripe size: 131072
Newest: 3
NoHot: No
Hardcoded provided: