there several guests running on this host but this is the only 14.04. guest. its used to provide a klolab server in a small company environment. 

lsb_release -rd
Description:	Ubuntu 14.04.3 LTS
Release:	14.04

...
[   52.815971] audit: type=1400 audit(1446640264.595:11): apparmor="STATUS" operation="profile_replace" profile="unconfined" name="/usr/lib/NetworkManager/nm-dhcp-client.action" pid=807 comm="apparmor_parser"
[ 1387.716628] blk_update_request: I/O error, dev vda, sector 7310848
[ 1387.716667] BTRFS: bdev /dev/vda1 errs: wr 1, rd 0, flush 0, corrupt 0, gen 0
[ 1387.716742] blk_update_request: I/O error, dev vda, sector 7310880
[ 1387.716768] BTRFS: bdev /dev/vda1 errs: wr 2, rd 0, flush 0, corrupt 0, gen 0
[ 1392.020693] blk_update_request: I/O error, dev vda, sector 1379968
[ 1392.020735] BTRFS: bdev /dev/vda1 errs: wr 3, rd 0, flush 0, corrupt 0, gen 0
[ 1392.020852] blk_update_request: I/O error, dev vda, sector 3477120
[ 1392.020864] BTRFS: bdev /dev/vda1 errs: wr 4, rd 0, flush 0, corrupt 0, gen 0
[ 1392.020918] blk_update_request: I/O error, dev vda, sector 1380096
[ 1392.020928] BTRFS: bdev /dev/vda1 errs: wr 5, rd 0, flush 0, corrupt 0, gen 0
[ 1392.020978] blk_update_request: I/O error, dev vda, sector 3477248
[ 1392.020988] BTRFS: bdev /dev/vda1 errs: wr 6, rd 0, flush 0, corrupt 0, gen 0
[ 1392.021040] blk_update_request: I/O error, dev vda, sector 1380224
[ 1392.021054] BTRFS: bdev /dev/vda1 errs: wr 7, rd 0, flush 0, corrupt 0, gen 0
[ 1392.021097] blk_update_request: I/O error, dev vda, sector 3477376
[ 1392.021104] BTRFS: bdev /dev/vda1 errs: wr 8, rd 0, flush 0, corrupt 0, gen 0
[ 1392.021157] blk_update_request: I/O error, dev vda, sector 1380352
[ 1392.021167] BTRFS: bdev /dev/vda1 errs: wr 9, rd 0, flush 0, corrupt 0, gen 0
[ 1392.021219] blk_update_request: I/O error, dev vda, sector 3477504
[ 1392.021250] BTRFS: bdev /dev/vda1 errs: wr 10, rd 0, flush 0, corrupt 0, gen 0
[ 1392.024316] BTRFS: error (device vda1) in btrfs_commit_transaction:2010: errno=-5 IO failure (Error while writing out transaction)
[ 1392.024335] BTRFS info (device vda1): forced readonly
[ 1392.024337] BTRFS warning (device vda1): Skipping commit of aborted transaction.
[ 1392.024339] ------------[ cut here ]------------
[ 1392.024421] WARNING: CPU: 0 PID: 156 at /build/linux-lts-vivid-Nr0FoT/linux-lts-vivid-3.19.0/fs/btrfs/super.c:260 __btrfs_abort_transaction+0x54/0x130 [btrfs]()
[ 1392.024422] BTRFS: Transaction aborted (error -5)
[ 1392.024424] Modules linked in: snd_hda_codec_generic qxl ppdev snd_hda_intel snd_hda_controller snd_hda_codec snd_hwdep ttm kvm_intel drm_kms_helper snd_pcm serio_raw snd_timer kvm parport_pc pvpanic lp snd drm i2c_piix4 mac_hid soundcore 8250_fintek parport btrfs xor raid6_pq psmouse pata_acpi floppy
[ 1392.024441] CPU: 0 PID: 156 Comm: btrfs-transacti Not tainted 3.19.0-31-generic #36~14.04.1-Ubuntu
[ 1392.024442] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.7.5-20150306_163512-brownie 04/01/2014
[ 1392.024444]  ffffffffc0190f40 ffff880059b1fc58 ffffffff817af3fb 0000000000000000
[ 1392.024446]  ffff880059b1fca8 ffff880059b1fc98 ffffffff81074daa ffff880059b1fcb8
[ 1392.024448]  ffff88013af0c000 ffff880036757800 00000000fffffffb ffffffffc018d370
[ 1392.024450] Call Trace:
[ 1392.024506]  [<ffffffff817af3fb>] dump_stack+0x45/0x57
[ 1392.024533]  [<ffffffff81074daa>] warn_slowpath_common+0x8a/0xc0
[ 1392.024536]  [<ffffffff81074e26>] warn_slowpath_fmt+0x46/0x50
[ 1392.024548]  [<ffffffff810cad19>] ? vprintk_default+0x29/0x40
[ 1392.024556]  [<ffffffffc00e0f14>] __btrfs_abort_transaction+0x54/0x130 [btrfs]
[ 1392.024568]  [<ffffffffc010e1ee>] cleanup_transaction+0x6e/0x2b0 [btrfs]
[ 1392.024572]  [<ffffffff810b4e30>] ? prepare_to_wait_event+0x110/0x110
[ 1392.024573]  [<ffffffff810b48c8>] ? __wake_up+0x48/0x60
[ 1392.024584]  [<ffffffffc010ef15>] btrfs_commit_transaction+0x295/0xa30 [btrfs]
[ 1392.024594]  [<ffffffffc010a9d5>] transaction_kthread+0x1b5/0x240 [btrfs]
[ 1392.024607]  [<ffffffffc010a820>] ? btrfs_cleanup_transaction+0x570/0x570 [btrfs]
[ 1392.024611]  [<ffffffff81093822>] kthread+0xd2/0xf0
[ 1392.024613]  [<ffffffff81093750>] ? kthread_create_on_node+0x1c0/0x1c0
[ 1392.024623]  [<ffffffff817b6d18>] ret_from_fork+0x58/0x90
[ 1392.024626]  [<ffffffff81093750>] ? kthread_create_on_node+0x1c0/0x1c0
[ 1392.024627] ---[ end trace 947f531859156e9f ]---
[ 1392.024629] BTRFS: error (device vda1) in cleanup_transaction:1670: errno=-5 IO failure
[ 1392.024664] BTRFS info (device vda1): delayed_refs has NO entry
[ 1392.024755] BTRFS info (device vda1): delayed_refs has NO entry
w@m:~$ 

fstab:
# <file system> <mount point>   <type>  <options>       <dump>  <pass>
# / was on /dev/vda1 during installation
UUID=856f7420-xxxx-xxxx-xxxx-3ace68a507a2 /               btrfs	defaults,compress=lzo,space_cache,subvol=@ 0       1
# /home was on /dev/vda1 during installation
UUID=856f7420-xxxx-xxxx-xxxx-3ace68a507a2 /home           btrfs defaults,compress=lzo,space_cache,subvol=@home 0       2
# swap was on /dev/vda5 during installation
UUID=7813ea97-xxxx-xxxx-xxxx-9fc9120d6c75 none            swap    sw              0       0
# kolab
UUID=856f7420-xxxx-xxxx-xxxx-3ace68a507a2 /var/           btrfs defaults,compress=lzo,space_cache,subvolid=261 0       2

w@m:~$ uname -a
Linux XXX 3.19.0-31-generic #36~14.04.1-Ubuntu SMP Thu Oct 8 10:21:08 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux

btrfs-tools:
Btrfs v3.12

sudo lspci -vnvn
[sudo] password for xx: 
sudo: /var/lib/sudo/xx/1 konnte nicht geöffnet werden: Das Dateisystem ist nur lesbar
00:00.0 Host bridge [0600]: Intel Corporation 440FX - 82441FX PMC [Natoma] [8086:1237] (rev 02)
	Subsystem: Red Hat, Inc Qemu virtual machine [1af4:1100]
	Control: I/O+ Mem+ BusMaster- SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR+ FastB2B- DisINTx-
	Status: Cap- 66MHz- UDF- FastB2B- ParErr- DEVSEL=fast >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx-

00:01.0 ISA bridge [0601]: Intel Corporation 82371SB PIIX3 ISA [Natoma/Triton II] [8086:7000]
	Subsystem: Red Hat, Inc Qemu virtual machine [1af4:1100]
	Control: I/O+ Mem+ BusMaster- SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR+ FastB2B- DisINTx-
	Status: Cap- 66MHz- UDF- FastB2B- ParErr- DEVSEL=medium >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx-

00:01.1 IDE interface [0101]: Intel Corporation 82371SB PIIX3 IDE [Natoma/Triton II] [8086:7010] (prog-if 80 [Master])
	Subsystem: Red Hat, Inc Qemu virtual machine [1af4:1100]
	Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR+ FastB2B- DisINTx-
	Status: Cap- 66MHz- UDF- FastB2B+ ParErr- DEVSEL=medium >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx-
	Latency: 0
	Region 0: [virtual] Memory at 000001f0 (32-bit, non-prefetchable) [size=8]
	Region 1: [virtual] Memory at 000003f0 (type 3, non-prefetchable)
	Region 2: [virtual] Memory at 00000170 (32-bit, non-prefetchable) [size=8]
	Region 3: [virtual] Memory at 00000370 (type 3, non-prefetchable)
	Region 4: I/O ports at c120 [size=16]
	Kernel driver in use: ata_piix

00:01.3 Bridge [0680]: Intel Corporation 82371AB/EB/MB PIIX4 ACPI [8086:7113] (rev 03)
	Subsystem: Red Hat, Inc Qemu virtual machine [1af4:1100]
	Control: I/O+ Mem+ BusMaster- SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR+ FastB2B- DisINTx-
	Status: Cap- 66MHz- UDF- FastB2B+ ParErr- DEVSEL=medium >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx-
	Interrupt: pin A routed to IRQ 9
	Kernel driver in use: piix4_smbus

00:02.0 VGA compatible controller [0300]: Red Hat, Inc. QXL paravirtual graphic card [1b36:0100] (rev 04) (prog-if 00 [VGA controller])
	Subsystem: Red Hat, Inc QEMU Virtual Machine [1af4:1100]
	Control: I/O+ Mem+ BusMaster- SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR+ FastB2B- DisINTx-
	Status: Cap- 66MHz- UDF- FastB2B- ParErr- DEVSEL=fast >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx-
	Interrupt: pin A routed to IRQ 10
	Region 0: Memory at f4000000 (32-bit, non-prefetchable) [size=64M]
	Region 1: Memory at f8000000 (32-bit, non-prefetchable) [size=64M]
	Region 2: Memory at fc054000 (32-bit, non-prefetchable) [size=8K]
	Region 3: I/O ports at c040 [size=32]
	Expansion ROM at fc040000 [disabled] [size=64K]
	Kernel driver in use: qxl

00:03.0 Ethernet controller [0200]: Red Hat, Inc Virtio network device [1af4:1000]
	Subsystem: Red Hat, Inc Device [1af4:0001]
	Physical Slot: 3
	Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR+ FastB2B- DisINTx+
	Status: Cap+ 66MHz- UDF- FastB2B- ParErr- DEVSEL=fast >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx-
	Latency: 0
	Interrupt: pin A routed to IRQ 11
	Region 0: I/O ports at c060 [size=32]
	Region 1: Memory at fc056000 (32-bit, non-prefetchable) [size=4K]
	Expansion ROM at fc000000 [disabled] [size=256K]
	Capabilities: [40] MSI-X: Enable+ Count=3 Masked-
		Vector table: BAR=1 offset=00000000
		PBA: BAR=1 offset=00000800
	Kernel driver in use: virtio-pci

00:04.0 Audio device [0403]: Intel Corporation 82801FB/FBM/FR/FW/FRW (ICH6 Family) High Definition Audio Controller [8086:2668] (rev 01)
	Subsystem: Red Hat, Inc QEMU Virtual Machine [1af4:1100]
	Physical Slot: 4
	Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR+ FastB2B- DisINTx+
	Status: Cap+ 66MHz- UDF- FastB2B- ParErr- DEVSEL=fast >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx-
	Latency: 0
	Interrupt: pin A routed to IRQ 31
	Region 0: Memory at fc050000 (32-bit, non-prefetchable) [size=16K]
	Capabilities: [60] MSI: Enable+ Count=1/1 Maskable- 64bit+
		Address: 00000000fee00000  Data: 40b1
	Kernel driver in use: snd_hda_intel

00:05.0 Communication controller [0780]: Red Hat, Inc Virtio console [1af4:1003]
	Subsystem: Red Hat, Inc Device [1af4:0003]
	Physical Slot: 5
	Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR+ FastB2B- DisINTx+
	Status: Cap+ 66MHz- UDF- FastB2B- ParErr- DEVSEL=fast >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx-
	Latency: 0
	Interrupt: pin A routed to IRQ 10
	Region 0: I/O ports at c080 [size=32]
	Region 1: Memory at fc057000 (32-bit, non-prefetchable) [size=4K]
	Capabilities: [40] MSI-X: Enable+ Count=2 Masked-
		Vector table: BAR=1 offset=00000000
		PBA: BAR=1 offset=00000800
	Kernel driver in use: virtio-pci

00:06.0 USB controller [0c03]: Intel Corporation 82801I (ICH9 Family) USB UHCI Controller #1 [8086:2934] (rev 03) (prog-if 00 [UHCI])
	Subsystem: Red Hat, Inc QEMU Virtual Machine [1af4:1100]
	Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR+ FastB2B- DisINTx-
	Status: Cap- 66MHz- UDF- FastB2B- ParErr- DEVSEL=fast >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx-
	Latency: 0
	Interrupt: pin A routed to IRQ 10
	Region 4: I/O ports at c0a0 [size=32]
	Kernel driver in use: uhci_hcd

00:06.1 USB controller [0c03]: Intel Corporation 82801I (ICH9 Family) USB UHCI Controller #2 [8086:2935] (rev 03) (prog-if 00 [UHCI])
	Subsystem: Red Hat, Inc QEMU Virtual Machine [1af4:1100]
	Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR+ FastB2B- DisINTx-
	Status: Cap- 66MHz- UDF- FastB2B- ParErr- DEVSEL=fast >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx-
	Latency: 0
	Interrupt: pin B routed to IRQ 11
	Region 4: I/O ports at c0c0 [size=32]
	Kernel driver in use: uhci_hcd

00:06.2 USB controller [0c03]: Intel Corporation 82801I (ICH9 Family) USB UHCI Controller #3 [8086:2936] (rev 03) (prog-if 00 [UHCI])
	Subsystem: Red Hat, Inc QEMU Virtual Machine [1af4:1100]
	Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR+ FastB2B- DisINTx-
	Status: Cap- 66MHz- UDF- FastB2B- ParErr- DEVSEL=fast >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx-
	Latency: 0
	Interrupt: pin C routed to IRQ 11
	Region 4: I/O ports at c0e0 [size=32]
	Kernel driver in use: uhci_hcd

00:06.7 USB controller [0c03]: Intel Corporation 82801I (ICH9 Family) USB2 EHCI Controller #1 [8086:293a] (rev 03) (prog-if 20 [EHCI])
	Subsystem: Red Hat, Inc QEMU Virtual Machine [1af4:1100]
	Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR+ FastB2B- DisINTx-
	Status: Cap- 66MHz- UDF- FastB2B- ParErr- DEVSEL=fast >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx-
	Latency: 0, Cache Line Size: 64 bytes
	Interrupt: pin D routed to IRQ 10
	Region 0: Memory at fc058000 (32-bit, non-prefetchable) [size=4K]
	Kernel driver in use: ehci-pci

00:07.0 SCSI storage controller [0100]: Red Hat, Inc Virtio block device [1af4:1001]
	Subsystem: Red Hat, Inc Device [1af4:0002]
	Physical Slot: 7
	Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR+ FastB2B- DisINTx+
	Status: Cap+ 66MHz- UDF- FastB2B- ParErr- DEVSEL=fast >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx-
	Latency: 0
	Interrupt: pin A routed to IRQ 11
	Region 0: I/O ports at c000 [size=64]
	Region 1: Memory at fc059000 (32-bit, non-prefetchable) [size=4K]
	Capabilities: [40] MSI-X: Enable+ Count=2 Masked-
		Vector table: BAR=1 offset=00000000
		PBA: BAR=1 offset=00000800
	Kernel driver in use: virtio-pci

00:08.0 Unclassified device [00ff]: Red Hat, Inc Virtio memory balloon [1af4:1002]
	Subsystem: Red Hat, Inc Device [1af4:0005]
	Physical Slot: 8
	Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR+ FastB2B- DisINTx-
	Status: Cap- 66MHz- UDF- FastB2B- ParErr- DEVSEL=fast >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx-
	Latency: 0
	Interrupt: pin A routed to IRQ 11
	Region 0: I/O ports at c100 [size=32]
	Kernel driver in use: virtio-pci