[linux-lvm] lvcreate: adding devices causes an alignment inconsistencies

[Bernhard Sulzer]

I wanted to create a raid5 array from 3x 7.3TiB drives but whatever I 
do, I seemingly can't align the devices in my lvm raid. Am I doing it 
wrong, or may there be a bug hiding somewhere?

# sudo vgcreate test --dataalignment 1M /dev/sd{c,d,e}
   Volume group "test" successfully created

# sudo lvcreate --type raid5 -L 4T --nosync -n test_data test
   Using default stripesize 64.00 KiB.
   WARNING: New raid5 won't be synchronised. Don't read what you didn't 
write!
   Logical volume "test_data" created.

As far as output from lvm commands is concerned, it all looks fine to 
me. But why, when looking at lsblk is there so much strange alignment 
going on?Is this normal or should I be concerned? (I don't know what 
performance I should expect with my setup so I can't say anything about 
that). Note, that the same thing happens when I try to create a raid0

# lsblk -t
NAME                      ALIGNMENT MIN-IO OPT-IO PHY-SEC LOG-SEC ROTA 
SCHED       RQ-SIZE  RA WSAME
sdc                               0   4096      0    4096 512    1 
mq-deadline      60 128   32M
├─test-test_data_rmeta_0          0   4096      0    4096 512    
1                 128 128   32M
│ └─test-test_data               -1  65536 131072    4096 512    
1                 128 384    0B
└─test-test_data_rimage_0         0   4096      0    4096 512    
1                 128 128   32M
   └─test-test_data               -1  65536 131072    4096 512    
1                 128 384    0B
sdd                               0   4096      0    4096 512    1 
mq-deadline      60 128   32M
├─test-test_data_rmeta_1          0   4096      0    4096 512    
1                 128 128   32M
│ └─test-test_data               -1  65536 131072    4096 512    
1                 128 384    0B
└─test-test_data_rimage_1         0   4096      0    4096 512    
1                 128 128   32M
   └─test-test_data               -1  65536 131072    4096 512    
1                 128 384    0B
sde                               0   4096      0    4096 512    1 
mq-deadline      60 128   32M
├─test-test_data_rmeta_2        512   4096      0    4096 512    
1                 128 128   32M
│ └─test-test_data               -1  65536 131072    4096 512    
1                 128 384    0B
└─test-test_data_rimage_2       512   4096      0    4096 512    
1                 128 128   32M

# dmesg -wH
[  +0.275210] device-mapper: raid: Superblocks created for new raid set
[  +0.002796] md/raid:mdX: device dm-1 operational as raid disk 0
[  +0.000004] md/raid:mdX: device dm-3 operational as raid disk 1
[  +0.000002] md/raid:mdX: device dm-5 operational as raid disk 2
[  +0.000801] md/raid:mdX: raid level 5 active with 3 out of 3 devices, 
algorithm 2
[  +0.010185] device-mapper: table: 254:6: adding target device dm-5 
caused an alignment inconsistency: physical_block_size=4096, 
logical_block_size=512, alignment_offset=512, start=0
[  +0.000005] device-mapper: table: 254:6: adding target device dm-5 
caused an alignment inconsistency: physical_block_size=4096, 
logical_block_size=512, alignment_offset=512, start=0
[  +0.000084] device-mapper: table: 254:6: adding target device dm-5 
caused an alignment inconsistency: physical_block_size=4096, 
logical_block_size=512, alignment_offset=512, start=0
[  +0.000003] device-mapper: table: 254:6: adding target device dm-5 
caused an alignment inconsistency: physical_block_size=4096, 
logical_block_size=512, alignment_offset=512, start=0
[  +0.070102] mdX: bitmap file is out of date, doing full recovery


Platform:
Arch Linux 5.6.0-rc7-1-git-00151-g67d584e33e54 (also tested with Debian 
on 4.19, same results)
LVM version:     2.02.186(2) (2019-08-27)
Library version: 1.02.164 (2019-08-27)
Driver version:  4.42.0


Any advice would be much appreciated, thanks