Re: Requesting assistance recovering RAID-5 array

Daniel Jones
2020-03-31T00:51:59Z

Greetings Wol,

> Don't even THINK of --create until the experts have chimed in !!!

Yes, I have had impure thoughts, but fortunately (?) I've done nothing
yet to intentionally write to the drives.

> If your drives are 1TB, I would *seriously* consider getting hold of a 4TB drive - they're not expensive - to make a backup. And read up on overlays.

The array drives are 10TB each. Understand the concept of overlays in
general (have used them in a container context) and have skimmed the
wiki, but not yet acted.

> The lsdrv information is crucial - that recovers pretty much all the config information that is available

Attached.

$ ./lsdrv
PCI [pata_marvell] 02:00.0 IDE interface: Marvell Technology Group
Ltd. 88SE6101/6102 single-port PATA133 interface (rev b2)
└scsi 0:x:x:x [Empty]
PCI [ahci] 00:1f.2 SATA controller: Intel Corporation 82801JI (ICH10
Family) SATA AHCI Controller
├scsi 2:0:0:0 ATA M4-CT256M4SSD2 {0000000012050904283E}
│└sda 238.47g [8:0] Partitioned (dos)
│ ├sda1 500.00m [8:1] xfs {8ed274ce-4cf6-4804-88f8-0213c002a716}
│ │└Mounted as /dev/sda1 @ /boot
│ └sda2 237.99g [8:2] PV LVM2_member 237.92g used, 64.00m free
{kn8lMS-0Cy8-xpsR-QRTk-CTRG-Eh1J-lmtfws}
│ └VG centos_hulk 237.98g 64.00m free {P5MVrD-UMGG-0IO9-zFNq-8zd2-lycX-oYqe5L}
│ ├dm-2 185.92g [253:2] LV home xfs {39075ece-de0a-4ace-b291-cc22aff5a4b2}
│ │└Mounted as /dev/mapper/centos_hulk-home @ /home
│ ├dm-0 50.00g [253:0] LV root xfs {68ffae87-7b51-4392-b3b8-59a7aa13ea68}
│ │└Mounted as /dev/mapper/centos_hulk-root @ /
│ └dm-1 2.00g [253:1] LV swap swap {f2da9893-93f0-42a1-ba86-5f3b3a72cc9b}
├scsi 3:0:0:0 ATA WDC WD100EMAZ-00 {1DGVH01Z}
│└sdb 9.10t [8:16] Partitioned (gpt)
├scsi 4:0:0:0 ATA WDC WD100EMAZ-00 {2YJ2XMPD}
│└sdc 9.10t [8:32] MD raid5 (4) inactive 'hulk:0'
{423d9a8e-636a-5f08-56ec-bd90282e478b}
├scsi 5:0:0:0 ATA WDC WD100EMAZ-00 {2YJDR8LD}
│└sdd 9.10t [8:48] Partitioned (gpt)
└scsi 6:0:0:0 ATA WDC WD100EMAZ-00 {JEHRKH2Z}
└sde 9.10t [8:64] Partitioned (gpt)

Cheers,
DJ

On Mon, Mar 30, 2020 at 6:24 PM antlists <antlists@youngman.org.uk> wrote:
>
> On 31/03/2020 01:04, Daniel Jones wrote:
> > I am genuinely over my head at this point and unsure how to proceed.
> > My logic tells me the best choice is to attempt a --create to try to
> > rebuild the missing superblocks, but I'm not clear if I should try
> > devices=4 (the true size of the array) or devices=3 (the size it was
> > last operating in). I'm also not sure of what device order to use
> > since I have likely scrambled /dev/sd[bcde] and am concerned about
> > what happens when I bring the previously disable drive back into the
> > array.
>
> Don't even THINK of --create until the experts have chimed in !!!
>
> https://raid.wiki.kernel.org/index.php/Linux_Raid#When_Things_Go_Wrogn
>
> The lsdrv information is crucial - that recovers pretty much all the
> config information that is available, and massively increases the
> chances of a successful --create, if you do have to go down that route...
>
> If your drives are 1TB, I would *seriously* consider getting hold of a
> 4TB drive - they're not expensive - to make a backup. And read up on
> overlays.
>
> Hopefully we can recover your data without too much grief, but this will
> all help.
>
> Cheers,
> Wol