# mdadm RAID autodetect isn't autodetecting

## theosib

I have two pairs of drives, each in RAID1 configuration.  The partitions are marked 0xfd, which is RAID autodetect.  The drive with the root and boot partitions is automatically assembled correctly.  But with the other pair of drives, this isn't happening.

I can get it to find and assemble the array with the command "mdadm --assemble --scan".  Then the node gets created.  But isn't this supposed to happen on boot?  Why isn't it happening and what can do to fix it?  I'd like this to assemble and mount on boot.

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## theosib

First I manually assembled the array and made sure it was up.  Then I tried creating a mdadm.conf file with this:

mdadm --detail --scan > /etc/mdadm.conf

Then I rebooted.  It STILL didn't assemble.  What's going on here?

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## theosib

Apparently, in order to have arrays assemble on boot, they must have metadata version 0.9.  I rebuilt the array with the older metadata version, and now it works just fine, and completely automatic.

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