Passthrough disk to windows showing wrong partitioning?

Herjar

Member
Mar 12, 2021
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Hi. I currently have a server running Windows 10. For the data disks I am using bitlocker, snapraid and drivepool. I am running many services and want to test moving to proxmox. Most can be run on linux, but I am not ready to move all the data disks to zfs yet. I have ~45 TB now and not much free space. I need to buy more disks to start moving stuff. So my thought was to image my server and start a Windows vm, share the disk pool from the vm and then moving services out of it as I go.

I used clonezilla to copy my server to proxmox and got it running (after lots of issues with boot partition errors). I passed through all the disks to the vm and it almost works perfectly. Bitlocker opens the disks fine and I have a pool I can share on the network. However, I have a problem with one disk. All my disks are SATA, except for this one which is SAS. Could that be the reason?

If I boot into Windows (instead of proxmox), the disk works fine. Here is the info from diskpart:
diskpart_disk4.png

When I boot into proxmox the disk shows up ok. Output from lshw -class disk -class storage:

Code:
*-disk:2
          description: SCSI Disk
          product: MG07SCA12TA
          vendor: TOSHIBA
          physical id: 0.2.0
          bus info: scsi@4:0.2.0
          logical name: /dev/sdc
          version: 0101
          serial: Y8W0A00JFJCG
          size: 10TiB (12TB)
          capacity: 14TiB (16TB)
          capabilities: 7200rpm partitioned partitioned:dos
          configuration: ansiversion=6 logicalsectorsize=4096 sectorsize=4096 signature=08f2a1e4

The main difference I can see from the other disks is "description: SCSI Disk" and "capabilities: 7200rpm partitioned partitioned:dos". I don't understand why it says dos as is is using gpt. The other disks say ATA Disk and gpt partitioned.

gdisk -l /dev/sdc output:

Code:
GPT fdisk (gdisk) version 1.0.3

The protective MBR's 0xEE partition is oversized! Auto-repairing.

Partition table scan:
  MBR: protective
  BSD: not present
  APM: not present
  GPT: present

Found valid GPT with protective MBR; using GPT.
Disk /dev/sdc: 2929721344 sectors, 10.9 TiB
Model: MG07SCA12TA
Sector size (logical/physical): 4096/4096 bytes
Disk identifier (GUID): D0F31CA4-18FC-4384-A954-4683C62CB621
Partition table holds up to 128 entries
Main partition table begins at sector 2 and ends at sector 5
First usable sector is 6, last usable sector is 2929721338
Partitions will be aligned on 8-sector boundaries
Total free space is 507 sectors (2.0 MiB)

Number  Start (sector)    End (sector)  Size       Code  Name
   1               6            4095   16.0 MiB    0C01  Microsoft reserved ...
   2            4096       976725503   3.6 TiB     0700  Basic data partition
   3       976725504      2059320831   4.0 TiB     0700  Basic data partition
   4      2059320832      2929720831   3.2 TiB     0700  Basic data partition

fdisk -l /dev/sdc also says "Disklabel type: gpt". Why does lshw list it as "partitioned:dos"?

This is the id of the disk:
lrwxrwxrwx 1 root root 9 Mar 12 22:22 /dev/disk/by-id/scsi-3500003990863aa05 -> ../../sdc

So I passed it to the vm with:
qm set 102 --scsi12 /dev/disk/by-id/scsi-3500003990863aa05

It shows up in vm hardware ok:
vmdisk12.png

But when I start the vm it shows up like this in Windows disk manager:
diskmanager.png

I have no idea where to go from here. Anyone know what could be wrong?
 
Somehow qm setted a wrong size for your disk.
I would remove it from the vm config again, try an fsck on that disk and pass it again.

And check if the size is correct and not 11gb after you passed again with qm.
 
It is a 12TB disk, so is 11176G the wrong size? What should it be?

The file system is NTFS, so I was not sure if fsck was the best tool to fix problems? I tried booting back into normal Windows and use chksdk, but it didn't find any errors.

I did however find a fix for now. I used passthrough on the PCI controller instead of the disks. I have a standalone LSI SAS2308, so I can keep all the data disks on that controller. Now everything seems to work ok. Are there any drawbacks to passing the controller over the disks?
 
If you pass the pci controller, it is in theory even better... But it has the downside that everything plugged to that controller is passed through, so not everyone can do this xD
 
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