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"Data alignment must not exceed device size."

linux-lvm Richard W.M. Jones 3 participants 8 messages Apr 10, 2018

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Richard W.M. Jones

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#0 lore raw

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.

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Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
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#1 lore raw
Quoted 11 lines · 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".

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.

Signature · 4 lines
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
libguestfs lets you edit virtual machines.  Supports shell scripting,
bindings from many languages.  http://libguestfs.org
#2 lore raw

Dne 10.4.2018 v 16:00 Richard W.M. Jones napsal(a):

Quoted 30 lines · Richard W.M. Jones
Quoted 11 lines

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".

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

Quoted 8 lines

(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

author
#3 lore raw
Quoted 37 lines · Zdenek Kabelac

Dne 10.4.2018 v 16:00 Richard W.M. Jones napsal(a):

Quoted 36 lines · Richard W.M. Jones
Quoted 11 lines

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".

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
Quoted 7 lines
Quoted 2 lines

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.

Same thing with 4.16.0-300.fc28.x86_64:

Quoted 1 line

<rescue> cat /sys/block/sda/queue/minimum_io_size

33553920

Quoted 1 line

<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.

Signature · 5 lines
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
virt-df lists disk usage of guests without needing to install any
software inside the virtual machine.  Supports Linux and Windows.
http://people.redhat.com/~rjones/virt-df/
#4 lore raw

Dne 10.4.2018 v 16:49 Richard W.M. Jones napsal(a):

Quoted 19 lines · Zdenek Kabelac
Quoted 17 lines

Dne 10.4.2018 v 16:00 Richard W.M. Jones napsal(a):

Quoted 16 lines · Richard W.M. Jones
Quoted 11 lines

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".

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

Quoted 8 lines
Quoted 3 lines

Hi

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

Same thing with 4.16.0-300.fc28.x86_64:

Quoted 1 line

<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

#5 lore raw
In reply to Zdenek Kabelac
Quoted 41 lines · Zdenek Kabelac

Dne 10.4.2018 v 16:00 Richard W.M. Jones napsal(a):

Quoted 30 lines · Richard W.M. Jones
Quoted 11 lines

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".

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

Quoted 8 lines

(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.

Quoted 5 lines

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

#6 lore raw
In reply to Richard W.M. Jones

Dne 10.4.2018 v 16:00 Richard W.M. Jones napsal(a):

Quoted 19 lines · Richard W.M. Jones
Quoted 11 lines

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".

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

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

Quoted 7 lines

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

On the new / broken system:

==> /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

author
#7 lore raw

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 <[email protected]>
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.

Signature · 5 lines
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
virt-df lists disk usage of guests without needing to install any
software inside the virtual machine.  Supports Linux and Windows.
http://people.redhat.com/~rjones/virt-df/