[linux-lvm] "Data alignment must not exceed device size."

[Richard W.M. Jones]

Recently in Fedora something changed that stops us from creating small
LVs for testing.

An example failure with a 64 MB partitioned disk:

# parted -s -- /dev/sda mklabel msdos mkpart primary 128s -128s
Warning: The resulting partition is not properly aligned for best performance: 128s % 65535s != 0s
# lvm pvcreate --force /dev/sda1
/dev/sda1: Data alignment must not exceed device size.
Format-specific initialisation of physical volume /dev/sda1 failed.
Failed to setup physical volume "/dev/sda1".

Obviously if I were to increase the beginning of the partition to
65536 sectors (32 MB) then there wouldn't be much space left for data.

Another possibly related issue happens if I use a 32 MB disk and leave
out the partition table (again, this used to work in Fedora up to recently):

# lvm pvcreate --force /dev/sda
# lvm vgcreate VG /dev/sda
# lvm lvcreate -l 100%FREE -n LV /dev/VG
Calculated size of logical volume is 0 extents. Needs to be larger.
guestfsd: error: Calculated size of logical volume is 0 extents. Needs to be larger.

I checked the lvm2 git repo and didn't see any recent changes which I
thought could affect this.

I'm not sure what component is responsible. I have two very similarly
configured machines where it works with one but not with the other.
The only difference seems to be the kernel:

Working:
kernel-4.15.0-0.rc8.git0.1.fc28.x86_64
device-mapper-1.02.146-1.fc28.x86_64
lvm2-2.02.177-1.fc28.x86_64

Not working:
kernel-4.16.0-0.rc4.git0.1.fc28.x86_64
device-mapper-1.02.146-1.fc28.x86_64
lvm2-2.02.177-1.fc28.x86_64

Rich.

[Richard W.M. Jones]

Post by Richard W.M. Jones
Recently in Fedora something changed that stops us from creating small
LVs for testing.
# parted -s -- /dev/sda mklabel msdos mkpart primary 128s -128s
Warning: The resulting partition is not properly aligned for best performance: 128s % 65535s != 0s
# lvm pvcreate --force /dev/sda1
/dev/sda1: Data alignment must not exceed device size.
Format-specific initialisation of physical volume /dev/sda1 failed.
Failed to setup physical volume "/dev/sda1".

Interestingly the alignment properties of the virtio-scsi virtual disk
has changed. On the working system:

==> /sys/block/sda/queue/minimum_io_size <==
512

==> /sys/block/sda/queue/optimal_io_size <==
0

On the new / broken system:

==> /sys/block/sda/queue/minimum_io_size <==
33553920

==> /sys/block/sda/queue/optimal_io_size <==
0

(all other settings were the same). I suppose this accounts for it,
and it could therefore be a problem with qemu rather than LVM.

Working: qemu-2.11.0-4.fc28.x86_64
Broken: qemu-2.12.0-0.5.rc1.fc29.x86_64

Alasdair Kergon asked me to run the lvm command with -vvvv and I've
attached those results.

Rich.

[Zdenek Kabelac]

Post by Richard W.M. Jones

Post by Richard W.M. Jones
Recently in Fedora something changed that stops us from creating small
LVs for testing.
# parted -s -- /dev/sda mklabel msdos mkpart primary 128s -128s
Warning: The resulting partition is not properly aligned for best performance: 128s % 65535s != 0s
# lvm pvcreate --force /dev/sda1
/dev/sda1: Data alignment must not exceed device size.
Format-specific initialisation of physical volume /dev/sda1 failed.
Failed to setup physical volume "/dev/sda1".

Interestingly the alignment properties of the virtio-scsi virtual disk
==> /sys/block/sda/queue/minimum_io_size <==
512
==> /sys/block/sda/queue/optimal_io_size <==
0
==> /sys/block/sda/queue/minimum_io_size <==
33553920
==> /sys/block/sda/queue/optimal_io_size <==
0
(all other settings were the same). I suppose this accounts for it,
and it could therefore be a problem with qemu rather than LVM.
Working: qemu-2.11.0-4.fc28.x86_64
Broken: qemu-2.12.0-0.5.rc1.fc29.x86_64
Alasdair Kergon asked me to run the lvm command with -vvvv and I've
attached those results.

Hi

Could you please retest first with official final release of 4.16 kernel.

There were some 'min()/max()' macro problems - maybe your rc4 build was affected.


Regards


Zdenek

[Richard W.M. Jones]

Post by Zdenek Kabelac

Post by Richard W.M. Jones

Post by Richard W.M. Jones
Recently in Fedora something changed that stops us from creating small
LVs for testing.
# parted -s -- /dev/sda mklabel msdos mkpart primary 128s -128s
Warning: The resulting partition is not properly aligned for best performance: 128s % 65535s != 0s
# lvm pvcreate --force /dev/sda1
/dev/sda1: Data alignment must not exceed device size.
Format-specific initialisation of physical volume /dev/sda1 failed.
Failed to setup physical volume "/dev/sda1".

Interestingly the alignment properties of the virtio-scsi virtual disk
==> /sys/block/sda/queue/minimum_io_size <==
512
==> /sys/block/sda/queue/optimal_io_size <==
0
==> /sys/block/sda/queue/minimum_io_size <==
33553920
==> /sys/block/sda/queue/optimal_io_size <==
0
(all other settings were the same). I suppose this accounts for it,
and it could therefore be a problem with qemu rather than LVM.
Working: qemu-2.11.0-4.fc28.x86_64
Broken: qemu-2.12.0-0.5.rc1.fc29.x86_64
Alasdair Kergon asked me to run the lvm command with -vvvv and I've
attached those results.

Hi
Could you please retest first with official final release of 4.16 kernel.
<rescue> cat /sys/block/sda/queue/minimum_io_size

33553920

Post by Zdenek Kabelac
<rescue> uname -a

Linux (none) 4.16.0-300.fc28.x86_64 #1 SMP Tue Apr 3 03:44:37 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux

I believe the faulty min/max macros were added after 4.16.0.

Rich.

[Zdenek Kabelac]

Post by Richard W.M. Jones

Post by Zdenek Kabelac

Post by Richard W.M. Jones

Post by Richard W.M. Jones
Recently in Fedora something changed that stops us from creating small
LVs for testing.
# parted -s -- /dev/sda mklabel msdos mkpart primary 128s -128s
Warning: The resulting partition is not properly aligned for best performance: 128s % 65535s != 0s
# lvm pvcreate --force /dev/sda1
/dev/sda1: Data alignment must not exceed device size.
Format-specific initialisation of physical volume /dev/sda1 failed.
Failed to setup physical volume "/dev/sda1".

Interestingly the alignment properties of the virtio-scsi virtual disk

Hi
Could you please retest first with official final release of 4.16 kernel.
<rescue> cat /sys/block/sda/queue/minimum_io_size

33553920

Forget to mention in my previous post - you should be able to override these
bad values reported from kernel with command line 'man pvcreate' options:
--dataalignment & --dataalignmentoffset


Regards

Zdenek

[Mike Snitzer]

On Tue, Apr 10 2018 at 10:43am -0400,

Post by Zdenek Kabelac

Post by Richard W.M. Jones

Post by Richard W.M. Jones
Recently in Fedora something changed that stops us from creating small
LVs for testing.
# parted -s -- /dev/sda mklabel msdos mkpart primary 128s -128s
Warning: The resulting partition is not properly aligned for best performance: 128s % 65535s != 0s
# lvm pvcreate --force /dev/sda1
/dev/sda1: Data alignment must not exceed device size.
Format-specific initialisation of physical volume /dev/sda1 failed.
Failed to setup physical volume "/dev/sda1".

Interestingly the alignment properties of the virtio-scsi virtual disk
==> /sys/block/sda/queue/minimum_io_size <==
512
==> /sys/block/sda/queue/optimal_io_size <==
0
==> /sys/block/sda/queue/minimum_io_size <==
33553920
==> /sys/block/sda/queue/optimal_io_size <==
0
(all other settings were the same). I suppose this accounts for it,
and it could therefore be a problem with qemu rather than LVM.
Working: qemu-2.11.0-4.fc28.x86_64
Broken: qemu-2.12.0-0.5.rc1.fc29.x86_64
Alasdair Kergon asked me to run the lvm command with -vvvv and I've
attached those results.

Hi
Could you please retest first with official final release of 4.16 kernel.
There were some 'min()/max()' macro problems - maybe your rc4 build was affected.

Uptream's min_not_zero() issue was introduced after 4.16 was released
(as part of the 4.17 merge window).

So not related (as Richard already pointed out).

Mike

[Zdenek Kabelac]

Post by Richard W.M. Jones

Post by Richard W.M. Jones
Recently in Fedora something changed that stops us from creating small
LVs for testing.
# parted -s -- /dev/sda mklabel msdos mkpart primary 128s -128s
Warning: The resulting partition is not properly aligned for best performance: 128s % 65535s != 0s
# lvm pvcreate --force /dev/sda1
/dev/sda1: Data alignment must not exceed device size.
Format-specific initialisation of physical volume /dev/sda1 failed.
Failed to setup physical volume "/dev/sda1".

Interestingly the alignment properties of the virtio-scsi virtual disk
==> /sys/block/sda/queue/minimum_io_size <==
512
==> /sys/block/sda/queue/optimal_io_size <==
0
==> /sys/block/sda/queue/minimum_io_size <==
33553920

What is actually this /dev/sda as device ?
scsi-0QEMU_QEMU_HARDDISK_drive-scsi0-0-0-0

Is this some qemu emulated storage ?

This reported value (33553920) doesn't really make sense - and testing over
loop device doesn't seem to give same result either.

Regards

Zdenek

[Richard W.M. Jones]

This turns out to be a bug in qemu 2.12-rc1.

It is fixed by this commit already upstream:

commit 37c51741892a89cf5710f5ac231091fb0a6352c7
Author: Fam Zheng <***@redhat.com>
Date: Wed Mar 28 00:41:41 2018 +0800

scsi-disk: Don't enlarge min_io_size to max_io_size

Some backends report big max_io_sectors. Making min_io_size the same
value in this case will make it impossible for guest to align memory,
therefore the disk may not be usable at all.

Do not enlarge them when they are zero.

Rich.