[ovirt-users] IO errors when adding new disk on iSCSI storage

Tue May 13 04:09:54 EDT 2014

Hi,

I have a new oVirt setup which is giving me some headache. I have one 
administration server running on CentOS 6.5, and two hosts also running 
CentOS 6.5. Storage is running on both NFS and iSCSI, but iSCSI is the 
preferred storage, running on a HP LeftHand server.

oVirt Engine Version: 3.4.0-1.el6

Administration server and hosts are all updated with latest packages 
both for CentOS and oVirt.

Both hosts are attached to a dedicated storage network with bonded 
interfaces:

# ifconfig bond1
bond1     Link encap:Ethernet  HWaddr AC:16:2D:8B:90:5E
           inet addr:192.168.40.160  Bcast:192.168.40.255 
Mask:255.255.255.0
           inet6 addr: fe80::ae16:2dff:fe8b:905e/64 Scope:Link
           UP BROADCAST RUNNING MASTER MULTICAST  MTU:1500  Metric:1
           RX packets:4149464 errors:0 dropped:0 overruns:0 frame:0
           TX packets:5590278 errors:0 dropped:0 overruns:0 carrier:0
           collisions:0 txqueuelen:0
           RX bytes:5387975600 (5.0 GiB)  TX bytes:6981018034 (6.5 GiB)

On the hosts the LUN is seen as:

scsi3 : iSCSI Initiator over TCP/IP
  connection1:0: detected conn error (1020)
  scsi 3:0:0:0: Direct-Access     LEFTHAND iSCSIDisk        a500 PQ: 0 
ANSI: 5
  sd 3:0:0:0: Attached scsi generic sg2 type 0
  sd 3:0:0:0: [sdb] 8589934592 512-byte logical blocks: (4.39 TB/4.00 TiB)
  sd 3:0:0:0: [sdb] Write Protect is off
  sd 3:0:0:0: [sdb] Mode Sense: 77 00 00 08
  sd 3:0:0:0: [sdb] Write cache: disabled, read cache: disabled, doesn't 
support DPO or FUA
   sdb: unknown partition table
   sd 3:0:0:0: [sdb] Attached SCSI disk

The iSCSI LUN I'm using is 4TB large, with 2.5TB free, according to the 
oVirt admin interface:

Size:	4095 GB
Available:	2551 GB
Used:	1544 GB
Allocated:	1540 GB
Over Allocation Ratio:	0%

Over to the problem:

On the virtual machine I'm testing on, I'm adding a new disk on the 
iSCSI storage server. The virtual machine is Debian 7.4 amd64. In this 
case 20GB large with thin provisioning. Then on the virtual machine I 
create a new logical volume group and disk:

Create a new partition with type 8e (Linux LVM):
fdisk /dev/vdc

Setup LVM:
pvcreate /dev/vdc1
vgcreate VGTEST /dev/vdc1
lvcreate -n lv_test -l 100%FREE VGTEST
mkfs.ext4 /dev/mapper/VGTEST-lv_test
mkdir /mnt/test
mount /dev/mapper/VGTEST-lv_test /mnt/test

Then I try writing to the new disk with f.ex dd:
dd if=/dev/zero of=/mnt/test/storfil bs=64k count=20480

Almost immediately oVirt will pause the machine with the following error 
message:

VM INT-KVM-SSM02 has paused due to no Storage space error.

dmesg on the virtual machine gives to following errors:

[353290.564507] Buffer I/O error on device dm-7, logical block 294774
[353290.564509] Buffer I/O error on device dm-7, logical block 294775
[353290.564511] EXT4-fs warning (device dm-7): ext4_end_bio:250: I/O 
error writing to inode 12 (offset 1039114240 size 520192 starting block 
294650)
[353290.564514] end_request: I/O error, dev vdc, sector 2362304
[353290.564516] Buffer I/O error on device dm-7, logical block 294776
[353290.564518] Buffer I/O error on device dm-7, logical block 294777
[353290.564519] Buffer I/O error on device dm-7, logical block 294778
[353290.564521] Buffer I/O error on device dm-7, logical block 294779
[353290.564522] Buffer I/O error on device dm-7, logical block 294780
[353290.564524] Buffer I/O error on device dm-7, logical block 294781
[353290.564525] Buffer I/O error on device dm-7, logical block 294782
[353290.564744] Buffer I/O error on device dm-7, logical block 294910
[353290.564746] Buffer I/O error on device dm-7, logical block 294911
[353290.564748] EXT4-fs warning (device dm-7): ext4_end_bio:250: I/O 
error writing to inode 12 (offset 1040154624 size 32768 starting block 
294904)
[353291.035703] EXT4-fs (dm-7): This should not happen!! Data will be lost
[353291.035705]
[353291.036280] JBD2: Detected IO errors while flushing file data on dm-7-8
[353291.036506] end_request: I/O error, dev vdc, sector 17043640
[353291.036509] end_request: I/O error, dev vdc, sector 17043640
[353291.036518] Aborting journal on device dm-7-8.
[353291.036734] end_request: I/O error, dev vdc, sector 17043456
[353291.036737] Buffer I/O error on device dm-7, logical block 2129920
[353291.036739] lost page write due to I/O error on dm-7
etc etc

If I try to do large writes on the existing disk on either the iSCSI or 
NFS storage there are no problems at all.

I have attached the engine.log from the administration server, and also 
the vdsm.log from the host

-- 
Morten A. Middelthon
Email: morten at flipp.net
Phone: +47 907 83 708
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