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mdadm raid inactive after reboot

Ruben Cardenal1709162194




In one of our new Xen servers, we have several quite huge attached disks. We're using 2 of them for a 28Tb RAID0 (yes, 0) for low importance backups. Created the soft raid, created the SR, and everything looks fine.


Then, reboot. And after, the raid is inactive. It has to be manually activated:


[15:49 monitor ~]# cat /proc/mdstat 
Personalities : 
md0 : inactive sdd[1] sdc[0]
      27344500736 blocks super 1.2
unused devices: <none>
[15:49 monitor ~]# mdadm --run /dev/md0
mdadm: started array /dev/md/0
[15:50 monitor ~]# cat /proc/mdstat 
Personalities : [raid0] 
md0 : active raid0 sdd[1] sdc[0]
      27344500736 blocks super 1.2 512k chunks

unused devices: <none>
[15:50 monitor ~]# 


(At this point, the SR can be repaired) 


Any idea why is this happening?



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1 minute ago, Mark Syms said:

Running XenServer on top of software mdadm RAID is not supported.


Hello Mark,


Well, truth the installation offers you the option of, precisely, creating a software raid... I guess we'll just have to be aware of that when rebooting that host. Made some test creating disks inside that SR and the data is retained.



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On 12/10/2020 at 11:55 AM, Tobias Kreidl said:

If you absolutely need software RAID to work, look into https://xcp-ng.org/ as an option .



Sorry to dig up an old thread, but.... Can you elaborate a bit?  What would XenServer have a problem with? Or are we just going to say 'no'? (which is fine I guess)

I've got two hosts, in a storage pool. One is empty; no VMs on it. Both attached to the same iSCSI host, and both using a software RAID 1 from the embedded RAID controller on the mother board, to boot.  I get a similar 'error' as the OP, but not sure it hasn't been that way the whole time.


# cat /proc/mdstat
Personalities : [raid1]
md126 : active raid1 sda[1] sdb[0]
      927881216 blocks super external:/md127/0 [2/2] [UU]
md127 : inactive sda[1](S) sdb[0](S)
      6306 blocks super external:imsm
unused devices: <none>


These have been up for over 1500 days.  They are currently on Xen Server 7.1, and we do have some others that are XCP-ng, so im not afraid of that.  The only reservation is that we've been held back to some older versions because of RAID hardware.  As this has NO actual RAID hardware, that shouldn't be a problem, just getting the imputes to actually do it...




Edited by Bryan Berndt
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XenServer has always "had a problem with" software raid. Not sure as to the specifics, but hardware raid is all that has ever been officially supported.

That is not to say that software raid won't work, but its apparently caused issues in the past so they just decided to not officially support it at all.




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