[linux-lvm] Filesystem corruption with LVM's pvmove onto a PV with a larger physical block size

[Ingo Franzki]

On 28.02.2019 10:48, Ilia Zykov wrote:
>>
>> Well, there are the following 2 commands:
>>
>> Get physical block size: 
>>  blockdev --getpbsz <device>
>> Get logical block size:
>>  blockdev --getbsz <device>
>>
>> Filesystems seem to care about the physical block size only, not the logical block size.
>>
>> So as soon as you have PVs with different physical block sizes (as reported by blockdev --getpbsz) I would be very careful...
> 
> Hello everybody.
> Maybe, I don’t understand what do you mean. What the logical block size
> mean? But on my machines(CentOS7), this utility get me the strange
> results (output reduced):
> 
>  smartctl -i /dev/sda; blockdev --getbsz --getpbsz /dev/sda
> Device Model:     INTEL SSDSC2KB480G8
> User Capacity:    480,103,981,056 bytes [480 GB]
> Sector Sizes:     512 bytes logical, 4096 bytes physical
> Rotation Rate:    Solid State Device
> 4096
> 4096
> 
>  smartctl -i /dev/sdb; blockdev --getbsz --getpbsz /dev/sdb
> Device Model:     HGST HUS722T2TALA604
> User Capacity:    2,000,398,934,016 bytes [2.00 TB]
> Sector Size:      512 bytes logical/physical
> Rotation Rate:    7200 rpm
> Form Factor:      3.5 inches
> 4096
> 512
> 
> As you see “–getbsz” forever 4096.
I also see logical block size to be 4096 for all devices on my system.
> But I think it must be forever 512.
> What does it mean?
I have seen the following description about logical and physical block sizes somewhere in the internet:
"Logical block sizes are the units used by the 'kernel' for read/write operations.
Physical block sizes are the units which 'disk controllers' use for read/write operations."

For the problem mentioned in this thread, the physical block size is what you are looking for.
> 
> Thank you.
> Ilia.
> 


-- 
Ingo Franzki
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