Re: Any way in LVM to deal with 512e vs 4Kn physical devices?

[Phillip Susi <phill@thesusis.net>]

Ilia Zykov <mail@service4.ru> writes:

> Hello.
>
> Sorry, I could be wrong, but I was encountered this problem a long time ago.
> You cannot transfer ext4 from a device with a phys sector 512 bite to a 
> device with phys 4k sector device.
> As far as I remember, ext4 uses this size to perform atomic operations.
> Because on the new disk it is not possible to perform an atomic 
> operation with data of 512 bytes,
> then it is impossible to transfer such a FS.
> See ENVIROMENTS for mkfs.ext4: "MKE2FS_DEVICE_SECTSIZE", 
> "MKE2FS_DEVICE_PHYS_SECTSIZE".

Ext[234] does IO in units of blocks.  In the days of 80 MB hard disks,
it could use a block size of 1 or 2 KB.  These days it pretty much
always uses 4 KB.  I'm almost certain that those environment variables
are to override what the kernel detects for testing purposes, and the
only thing mkfs does with this information is to force a 4K block size (
when that is the sector size ), even if the fs is small enough that it
otherwise would use 1 or 2.