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SATA hotplug + mdadm raid


I recently upgraded my home server to an HP ml30 tower server. It came with a 4 drive hotplug SATA cage. I loaded two old unused drives in it and installed Debian Stretch on it putting the drives in a software raid1 via the debian installer. My plan was once I got the new box up and running that I would shut off the old machine and use the drives from that, swapping them out one at a time and letting mdadm resync.

Before putting the new box into "production", I pulled the 2nd drive (sdb) to see what would happen (with the machine still running). Of course mdadm went into degraded mode with a one disk raid1. I slid the same drive back in and it came back as /dev/sdb. Later on, after a few reboots, I pulled the 2nd drive and swapped it with a drive from the old machine (it was also still up and running with mdadm raid1). However this time the new drive didn't come up as sdb, but as /dev/sdc. I set up the partitions the same as sda but I didn't join it to the mdadm array yet. I wasn't sure if joining as "sdc" and then on reboot having it come up possibly as "sdb" would mess up anything so I just rebooted. On reboot it came up as "sdb" and I joined it to the array and all was well.

But I still need to swap the first drive (sda) and I don't really want to have to reboot this time. So what can I do to ensure that once I pull the old drive and put in the new one that it comes back up as "sda"? Or does that even matter? (seems like it would..)


Samuel Smith

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