Virtual Disk with 4k sector size ?


I see multiple reference to it on Internet and this forum. It's seams to be possible to run kvm with 4k sector size using the `-set 'device.scsi0.physical_block_size=4096' -set 'device.scsi0.logical_block_size=4096'` in command line, but it doesn't seams to be possible to do it properly in proxmox.

So I'm asking here. Is it possible to reate a VirtualDisk in proxmox with 4k sector size ?


Famous Member
Feb 21, 2015
Nice question! I also wondered about that, too.

For all that wonder how to determine that:

cat /sys/block/sda/queue/hw_sector_size

Wenle Z

New Member
Jun 23, 2017
I would like to know as well. I map a physical drive from the Host ( Proxmox 5 ) to a virtual machine. While it works, and I can write and read to the physical disk, I notice it's very slow, at around 20mb write. I also had one instance where the partition became corrupted, and I had to use fsck on the host to correct the disk. I was not able to mount nor use fsck on the VM. So, is there a way to make the VM know this is a 4k sector drive?

root@pve:~# parted /dev/sdd 'print'
Model: ATA WDC WD80EFZX-68U (scsi)
Disk /dev/sdd: 8002GB
Sector size (logical/physical): 512B/4096B
Partition Table: gpt
Disk Flags:

Number  Start   End     Size    File system  Name   Flags
 1      1049kB  8002GB  8002GB  ext4         8TB_1


bash-4.3# parted /dev/sdd 'print'
Model: QEMU HARDDISK (scsi)
Disk /dev/sdd: 8002GB
Sector size (logical/physical): 512B/512B
Partition Table: gpt
Disk Flags:

Number  Start   End     Size    File system  Name   Flags
 1      1049kB  8002GB  8002GB  ext4         8TB_1


Renowned Member
Apr 19, 2017
Brasov, Romania
The problem is the fact that some hdd use some block size, but in reality it use another value. In this topic, I see different test cases (hdd directly exposed to the kvm or not - is only a supposition )
Anyway any disk with different
logical/physical like 512B/4096B I think is not usable for 4k usage. For example zfs have a special code who will try to detect/find if the hdd can use 512 B or anything else value(at the moment when the pool is made)
In the end the question is how we can know if a hdd it can use 4k or not.... In my own opinion , a good test is to put zfs on it, and then to find if zfs use for this hdd 4k or not. I want only to scratch the surface of this subject ... :)


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