I should say that all of my current diagnostic output is actually from
a virt running Debian 10 (Kernel 4.19.0), not the original Ubuntu
12.04. But the behavior is practically the same in both, and I'd
rather get it working on a modern system anyway.
-Chris
On Sun, May 16, 2021 at 9:16 PM Christopher Thomas <youkai@xxxxxxxxxxxxx> wrote:
>
> Hi all,
>
> I've updated my system & migrated my 3 raid5 component drives from the
> old to the new, but now can't reassemble the array - mdadm just
> doesn't recognize that these belong to an array at all.
>
> The scenario:
> For many years, I've run a raid5 array on a virtual Linux server
> (Ubuntu 12.04) in VirtualBox on a Windows 10 host, with 3 2.7TB drives
> attached to the virt in "Raw Disk" mode, and assembled into an array.
> I recently upgraded to a completely different physical machine, but
> still running Windows 10 and VirtualBox. I'm reasonably sure that the
> last time I shut it down, the array was clean. Or at they very least,
> the drives had superblocks. I plugged the old drives into it,
> migrated the virtual machine image to the new system, and attached
> them as raw disks, just as in the old system. And they show up as
> /dev/sd[b-d], as before. However, it's not recognized automatically
> as an array at boot, and manual attempts to assemble & start the array
> fail with 'no superblock'
>
> The closest I've found online as a solution is to --create the array
> again using the same parameters. But it sounds like if I don't get
> the drive order exactly the same, I'll lose the data. Other solutions
> hint at playing with the partition table, but I'm equally nervous
> about that. So I thought it was a good time to stop & ask for advice.
>
> The details:
>
> Here's my arrangement of disks now, where sd[bcd] are the components:
>
> ==========
> chris@ursula:~$ lsblk
> NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
> sda 8:0 0 20.1G 0 disk
> ├─sda1 8:1 0 19.2G 0 part /
> ├─sda2 8:2 0 1K 0 part
> └─sda5 8:5 0 976M 0 part [SWAP]
> sdb 8:16 0 2.7T 0 disk
> └─sdb1 8:17 0 128M 0 part
> sdc 8:32 0 2.7T 0 disk
> └─sdc1 8:33 0 128M 0 part
> sdd 8:48 0 2.7T 0 disk
> └─sdd1 8:49 0 128M 0 part
> sr0 11:0 1 1024M 0 rom
>
> chris@ursula:~$ sudo /sbin/fdisk -l
> Disk /dev/sda: 20.1 GiB, 21613379584 bytes, 42213632 sectors
> Disk model: VBOX HARDDISK
> Units: sectors of 1 * 512 = 512 bytes
> Sector size (logical/physical): 512 bytes / 512 bytes
> I/O size (minimum/optimal): 512 bytes / 512 bytes
> Disklabel type: dos
> Disk identifier: 0x4bbbafdf
>
> Device Boot Start End Sectors Size Id Type
> /dev/sda1 * 2048 40212479 40210432 19.2G 83 Linux
> /dev/sda2 40214526 42213375 1998850 976M 5 Extended
> /dev/sda5 40214528 42213375 1998848 976M 82 Linux swap / Solaris
>
>
> Disk /dev/sdb: 2.7 TiB, 3000592982016 bytes, 5860533168 sectors
> Disk model: VBOX HARDDISK
> Units: sectors of 1 * 512 = 512 bytes
> Sector size (logical/physical): 512 bytes / 512 bytes
> I/O size (minimum/optimal): 512 bytes / 512 bytes
> Disklabel type: gpt
> Disk identifier: 6489224B-FAF8-45E2-AB3D-C0D280F8E91E
>
> Device Start End Sectors Size Type
> /dev/sdb1 34 262177 262144 128M Microsoft reserved
>
>
> Disk /dev/sdc: 2.7 TiB, 3000592982016 bytes, 5860533168 sectors
> Disk model: VBOX HARDDISK
> Units: sectors of 1 * 512 = 512 bytes
> Sector size (logical/physical): 512 bytes / 512 bytes
> I/O size (minimum/optimal): 512 bytes / 512 bytes
> Disklabel type: gpt
> Disk identifier: 6497BDEB-A8D0-40D7-9CD2-D06018862F2B
>
> Device Start End Sectors Size Type
> /dev/sdc1 34 262177 262144 128M Microsoft reserved
>
>
> Disk /dev/sdd: 2.7 TiB, 3000592982016 bytes, 5860533168 sectors
> Disk model: VBOX HARDDISK
> Units: sectors of 1 * 512 = 512 bytes
> Sector size (logical/physical): 512 bytes / 512 bytes
> I/O size (minimum/optimal): 512 bytes / 512 bytes
> Disklabel type: gpt
> Disk identifier: 9DB2C3F2-F93D-4A6D-AE0E-CE28A8B8C4A2
>
> Device Start End Sectors Size Type
> /dev/sdd1 34 262177 262144 128M Microsoft reserved
> ==========
>
> Note: I always intended to use the whole disk, so I don't know why I
> would have created a single large partition on each, and I don't
> recall doing so. But it's been a while, so I just might not be
> remembering.
>
> Here's what happens when I try to do anything with it:
>
> ===========
> chris@ursula:~$ sudo /sbin/mdadm --verbose --assemble /dev/md0
> /dev/sdb /dev/sdc /dev/sdd
> mdadm: looking for devices for /dev/md0
> mdadm: Cannot assemble mbr metadata on /dev/sdb
> mdadm: /dev/sdb has no superblock - assembly aborted
>
> chris@ursula:~$ sudo /sbin/mdadm --examine /dev/sd[bcd]*
> /dev/sdb:
> MBR Magic : aa55
> Partition[0] : 4294967295 sectors at 1 (type ee)
> mdadm: No md superblock detected on /dev/sdb1.
> /dev/sdc:
> MBR Magic : aa55
> Partition[0] : 4294967295 sectors at 1 (type ee)
> mdadm: No md superblock detected on /dev/sdc1.
> /dev/sdd:
> MBR Magic : aa55
> Partition[0] : 4294967295 sectors at 1 (type ee)
> mdadm: No md superblock detected on /dev/sdd1.
> ======
>
> At some point on the old system, back when the array was still
> working, I did dump the results of Examine, which looked like this:
>
> ==========
> /dev/sdb:
> Magic : a92b4efc
> Version : 1.2
> Feature Map : 0x0
> Array UUID : 36205acf:993973ba:05712a13:ff75c031
> Name : ursula:0 (local to host ursula)
> Creation Time : Fri Apr 26 23:15:04 2013
> Raid Level : raid5
> Raid Devices : 3
>
> Avail Dev Size : 5860271024 (2794.40 GiB 3000.46 GB)
> Array Size : 5860270080 (5588.79 GiB 6000.92 GB)
> Used Dev Size : 5860270080 (2794.39 GiB 3000.46 GB)
> Data Offset : 262144 sectors
> Super Offset : 8 sectors
> State : active
> Device UUID : 8841770a:f653d990:d5db60a0:fe2e4276
>
> Update Time : Sun Jul 5 12:36:19 2020
> Checksum : 3a671053 - correct
> Events : 76713
>
> Layout : left-symmetric
> Chunk Size : 512K
>
> Device Role : Active device 2
> Array State : AAA ('A' == active, '.' == missing)
> /dev/sdc:
> Magic : a92b4efc
> Version : 1.2
> Feature Map : 0x0
> Array UUID : 36205acf:993973ba:05712a13:ff75c031
> Name : ursula:0 (local to host ursula)
> Creation Time : Fri Apr 26 23:15:04 2013
> Raid Level : raid5
> Raid Devices : 3
>
> Avail Dev Size : 5860271024 (2794.40 GiB 3000.46 GB)
> Array Size : 5860270080 (5588.79 GiB 6000.92 GB)
> Used Dev Size : 5860270080 (2794.39 GiB 3000.46 GB)
> Data Offset : 262144 sectors
> Super Offset : 8 sectors
> State : clean
> Device UUID : 87fd8496:95c9cd5e:5caaa28a:25f6ab04
>
> Update Time : Sat May 30 02:02:45 2020
> Checksum : ce4cd20 - correct
> Events : 76711
>
> Layout : left-symmetric
> Chunk Size : 512K
>
> Device Role : Active device 0
> Array State : AAA ('A' == active, '.' == missing)
> /dev/sdd:
> Magic : a92b4efc
> Version : 1.2
> Feature Map : 0x0
> Array UUID : 36205acf:993973ba:05712a13:ff75c031
> Name : ursula:0 (local to host ursula)
> Creation Time : Fri Apr 26 23:15:04 2013
> Raid Level : raid5
> Raid Devices : 3
>
> Avail Dev Size : 5860271024 (2794.40 GiB 3000.46 GB)
> Array Size : 5860270080 (5588.79 GiB 6000.92 GB)
> Used Dev Size : 5860270080 (2794.39 GiB 3000.46 GB)
> Data Offset : 262144 sectors
> Super Offset : 8 sectors
> State : active
> Device UUID : c796e484:b4ed6813:a97e0ce9:66a56758
>
> Update Time : Sun Jul 5 12:36:19 2020
> Checksum : 6235188e - correct
> Events : 76713
>
> Layout : left-symmetric
> Chunk Size : 512K
>
> Device Role : Active device 1
> Array State : AAA ('A' == active, '.' == missing)
> ==========
>
> Thank you for any ideas or guidance you can offer.
> -Chris
