xenserver

Citrix XenServer 6.0.2 Multipath Setup on Intel Modular Multi-Flex Server

1. Prerequisites

First of all, create at least one Storage Repository (SR) and one Virtual Disk (VD) in the Intel Management Module GUI where you will install the Citrix Xenserver Dom0 host. The VD needs to be more than 16Gb in size. Whether you install the host on sas or ssd makes no difference in performance for the guests. I installed my hosts to sas and saved valuable ssd space for guests. Assign your VD to the server you will install Xen to. Set affinity to SCM1 for all VD-s you create. Open the KVM session for the appropriate Compute Module and attach Xenserver installation iso. Power on the Compute Module.

 

2. Install Citrix Xenserver 6.0.2

Type ‘multipath’ on initial install prompt to begin installation with multipath support.

Choose the VD you just assigned to the Compute Module as installation target.

After installation is complete, you may see disk access errors during bootup, this is normal.

 

3. Install patched driver and change multipath.conf file

Original driver included with XenServer 6.0.2 is unstable wth multipathing.

I compiled a stable driver rpm with Citrix XenServer Driver Development Kit (DDK) from RedHat driver available on Intel site.

Note that this has been compiled against 6.0.2 and you may need to recompile if you use a more recent XenServer version.

Download the driver and multipath.conf file: scsi_dh_alua_intelmodular_cbvtrak.i386.tar.gz

Unpack the file:

tar -zxvf scsi_dh_alua_intelmodular_cbvtrak.i386.tar.gz

Install scsi_dh_alua driver rpm patched for Intel Modular Server.

The driver already exists so we have to force in order to replace it.

rpm -ivh --force scsi_dh_alua_intelmodular_cbvtrak.i386.rpm

Backup your current /etc/multipath.conf to /etc/multipath.conf.originalxs602:

cp /etc/multipath.conf /etc/multipath.conf.originalxs602

Move the multipath.conf file from the unpacked tar to the /etc folder:

mv multipath.conf /etc/multipath.conf

Warning: do not copy and paste the file contents as it can make the config file corrupt and thus failing server multipath setup.

Reboot

You may still see disk access errors during bootup, this is normal.

At this point you should already see both paths active, see my sample:

multipath -ll

Response:

2223700015563b1df dm-0 Intel,Multi-Flex
[size=16G][features=1 queue_if_no_path][hwhandler=0][rw]
\_ round-robin 0 [prio=50][active]
 \_ 0:0:0:0 sda 8:0   [active][ready]
\_ round-robin 0 [prio=1][enabled]
 \_ 0:0:1:0 sdb 8:16  [active][ready]

 

4. Make a new initial ramdisk

Backup your current initrd.img and initrd.kdump

mv initrd-$(uname -r).img initrd-$(uname -r).img.old
mv initrd-2.6.32.12-0.7.1.xs6.0.2.542.170665kdump.img initrd-2.6.32.12-0.7.1.xs6.0.2.542.170665kdump.img.old

Make new initial ramdisk by running both mkinitrd commands found in

cat initrd-$(uname -r).img.cmd
cat initrd-2.6.32.12-0.7.1.xs6.0.2.542.170665kdump.img.cmd

Reboot

You should see no more errors during bootup

Check your paths

multipath -ll

With one VD attached you shold see something like this:

22202000155fdb615 dm-0 Intel,Multi-Flex
[size=100G][features=1 queue_if_no_path][hwhandler=1 alua][rw]
\_ round-robin 0 [prio=50][active]
\_ 0:0:0:0 sda 8:0 [active][ready]
\_ round-robin 0 [prio=1][enabled]
\_ 0:0:1:0 sdb 8:16 [active][ready]

As you can see, sda is in use (active) and sdb is on standby (enabled).

 

4. Create and link other VD-s to the Compute Module

From Intel Intel GUI link VD-s to Compute Module.

In XenCenter right click on Pool – New SR – Hardware HBA.

Check your paths:

multipath -ll

Here is a sample response from my setup:

22202000155fdb615 dm-0 Intel,Multi-Flex
[size=100G][features=1 queue_if_no_path][hwhandler=1 alua][rw]
\_ round-robin 0 [prio=50][active]
\_ 0:0:2:0 sda 8:0 [active][ready]
\_ round-robin 0 [prio=1][enabled]
\_ 0:0:1:0 sdc 8:32 [active][ready]
222ac00015543fe63 dm-5 Intel,Multi-Flex
[size=420G][features=1 queue_if_no_path][hwhandler=1 alua][rw]
\_ round-robin 0 [prio=50][enabled]
\_ 0:0:2:10 sde 8:64 [active][ready]
\_ round-robin 0 [prio=1][enabled]
\_ 0:0:1:10 sdd 8:48 [active][ready]

 

5.  Modify your lvm.conf to filter out /dev/sd* when running commands: pvs, vgs, lvs

Find the line starting with ‘filter’ in /etc/lvm/lvm.conf

Edit it as follows:

filter = [ "r|/dev/sd.*|", "r|/dev/xvd.|", "r|/dev/VG_Xen.*/*|"]

 

6. Updating, patching, hotfixes

Running hotfix XS602E004 is safe (kernel is not updated).

Running hotfix XS602E005 is safe as update process will rebuild your initrd as well.

 

7. Failover testing on Intel Modular Server with multipathing

See my other post with successful filover tests with this configuration

Successful Failover Test Results – Multipathing on Intel Modular Multi-Flex Server with Citrix Xenserver 6.0.2

Initial setup

 

Both Storage Controller Modules attached and Intel Modular Server running on Citrix Xenserver 6.0.2 with patched dh_scsi_alua driver.

See my other blog post on how to set up stable multipathing on IMS with Citrix Xenserver 6.0.2

Initial multipath state:

[root@xenserver1 ~]# multipath -ll
22202000155fdb615 dm-0 Intel,Multi-Flex
[size=100G][features=1 queue_if_no_path][hwhandler=1 alua][rw]
\_ round-robin 0 [prio=50][active]
\_ 0:0:0:0 sda 8:0 [active][ready]
\_ round-robin 0 [prio=1][enabled]
\_ 0:0:1:0 sdb 8:16 [active][ready]

Note that I waited around 5 minutes after each SCM pull out / push back in order to let the system stabilize.

I did not reboot the host between these events.

Pull out SCM2 for the first time

 

Messages:

Apr 7 17:26:35 xenserver1 kernel: sd 0:0:1:0: [sdb] Synchronizing SCSI cache
Apr 7 17:26:35 xenserver1 kernel: sd 0:0:1:0: [sdb] Result: hostbyte=DID_NO_CONNECT driverbyte=DRIVER_OK
Apr 7 17:26:35 xenserver1 kernel: mptsas: ioc0: delete expander: num_phys 25, sas_addr (0x5001e671d12253ff)
Apr 7 17:26:35 xenserver1 kernel: mptbase: ioc0: LogInfo(0x31140000): Originator={PL}, Code={IO Executed}, SubCode(0x0000)
Apr 7 17:26:35 xenserver1 kernel: mptscsih: ioc0: ERROR – Received a mf that was already freed
Apr 7 17:26:35 xenserver1 kernel: mptscsih: ioc0: ERROR – req_idx=beaf req_idx_MR=43 mf=ec984980 mr=ec9825d0 sc=(null)
Apr 7 17:26:35 xenserver1 multipathd: sdb: remove path (operator)
Apr 7 17:26:35 xenserver1 multipathd: 22202000155fdb615: load table [0 209715200 multipath 1 queue_if_no_path 1 alua 1 1 round-robin 0 1 1 8:0 100]
Apr 7 17:26:35 xenserver1 multipathd: Path event for 22202000155fdb615, calling mpathcount
Apr 7 17:26:42 xenserver1 kernel: sd 0:0:0:0: alua: port group 00 state A supports touSnA

Multipath state:

[root@xenserver1 ~]# multipath -ll
22202000155fdb615 dm-0 Intel,Multi-Flex
[size=100G][features=1 queue_if_no_path][hwhandler=1 alua][rw]
\_ round-robin 0 [prio=50][active]
\_ 0:0:0:0 sda 8:0 [active][ready]

 

Push back SCM2 for the first time

 

Messages:

Apr 7 17:34:26 xenserver1 kernel: mptsas: ioc0: add expander: num_phys 25, sas_addr (0x5001e671d12253ff)
Apr 7 17:34:27 xenserver1 kernel: mptsas: ioc0: attaching ssp device: fw_channel 0, fw_id 1, phy 11, sas_addr 0x500015500002050a
Apr 7 17:34:27 xenserver1 kernel: target0:0:2: mptsas: ioc0: add device: fw_channel 0, fw_id 1, phy 11, sas_addr 0x500015500002050a
Apr 7 17:34:27 xenserver1 kernel: scsi 0:0:2:0: Direct-Access Intel Multi-Flex 0308 PQ: 0 ANSI: 5
Apr 7 17:34:27 xenserver1 kernel: scsi 0:0:2:0: mptscsih: ioc0: qdepth=64, tagged=1, simple=1, ordered=0, scsi_level=6, cmd_que=1
Apr 7 17:34:27 xenserver1 kernel: scsi 0:0:2:0: alua: supports explicit TPGS
Apr 7 17:34:27 xenserver1 kernel: scsi 0:0:2:0: alua: port group 01 rel port 06
Apr 7 17:34:27 xenserver1 kernel: scsi 0:0:2:0: alua: port group 01 state S supports touSnA
Apr 7 17:34:27 xenserver1 kernel: sd 0:0:2:0: Attached scsi generic sg1 type 0
Apr 7 17:34:27 xenserver1 kernel: sd 0:0:2:0: [sdb] 209715200 512-byte logical blocks: (107 GB/100 GiB)
Apr 7 17:34:27 xenserver1 kernel: sd 0:0:2:0: [sdb] Write Protect is off
Apr 7 17:34:27 xenserver1 kernel: sd 0:0:2:0: [sdb] Write cache: enabled, read cache: enabled, supports DPO and FUA
Apr 7 17:34:27 xenserver1 kernel: sdb:
Apr 7 17:34:27 xenserver1 kernel: ldm_validate_partition_table(): Disk read failed.
Apr 7 17:34:27 xenserver1 kernel: unable to read partition table
Apr 7 17:34:27 xenserver1 kernel: sd 0:0:2:0: [sdb] Attached SCSI disk
Apr 7 17:34:29 xenserver1 multipathd: sdb: add path (operator)
Apr 7 17:34:29 xenserver1 multipathd: 22202000155fdb615: load table [0 209715200 multipath 1 queue_if_no_path 1 alua 2 1 round-robin 0 1 1 8:0 100 round-robin 0 1 1
Apr 7 17:34:29 xenserver1 multipathd: Path event for 22202000155fdb615, calling mpathcount
Apr 7 17:34:43 xenserver1 kernel: sd 0:0:0:0: alua: port group 00 state A supports touSnA

Multipath state:

22202000155fdb615 dm-0 Intel,Multi-Flex
[size=100G][features=1 queue_if_no_path][hwhandler=1 alua][rw]
\_ round-robin 0 [prio=50][active]
\_ 0:0:0:0 sda 8:0 [active][ready]
\_ round-robin 0 [prio=1][enabled]
\_ 0:0:2:0 sdb 8:16 [active][ready]

 

Pull out SCM2 for the second time

 

Messages:

Apr 7 17:39:13 xenserver1 kernel: sd 0:0:2:0: [sdb] Synchronizing SCSI cache
Apr 7 17:39:13 xenserver1 kernel: sd 0:0:2:0: [sdb] Result: hostbyte=DID_NO_CONNECT driverbyte=DRIVER_OK
Apr 7 17:39:13 xenserver1 kernel: mptsas: ioc0: delete expander: num_phys 25, sas_addr (0x5001e671d12253ff)
Apr 7 17:39:13 xenserver1 multipathd: sdb: remove path (operator)
Apr 7 17:39:13 xenserver1 multipathd: 22202000155fdb615: load table [0 209715200 multipath 1 queue_if_no_path 1 alua 1 1 round-robin 0 1 1 8:0 100]
Apr 7 17:39:13 xenserver1 multipathd: Path event for 22202000155fdb615, calling mpathcount
Apr 7 17:39:14 xenserver1 kernel: mptbase: ioc0: LogInfo(0x31140000): Originator={PL}, Code={IO Executed}, SubCode(0x0000)
Apr 7 17:39:14 xenserver1 kernel: mptscsih: ioc0: ERROR – Received a mf that was already freed
Apr 7 17:39:14 xenserver1 kernel: mptscsih: ioc0: ERROR – req_idx=beaf req_idx_MR=d2 mf=ec989100 mr=ec9822b0 sc=(null)
Apr 7 17:39:16 xenserver1 kernel: sd 0:0:0:0: alua: port group 00 state A supports touSnA

Multipath state:

22202000155fdb615 dm-0 Intel,Multi-Flex
[size=100G][features=1 queue_if_no_path][hwhandler=1 alua][rw]
\_ round-robin 0 [prio=50][active]
\_ 0:0:0:0 sda 8:0 [active][ready]

Push back SCM2 for the second time

 

Messages:

Apr 7 17:47:36 xenserver1 kernel: mptsas: ioc0: add expander: num_phys 25, sas_addr (0x5001e671d12253ff)
Apr 7 17:47:37 xenserver1 kernel: mptsas: ioc0: attaching ssp device: fw_channel 0, fw_id 1, phy 11, sas_addr 0x500015500002050a
Apr 7 17:47:37 xenserver1 kernel: target0:0:3: mptsas: ioc0: add device: fw_channel 0, fw_id 1, phy 11, sas_addr 0x500015500002050a
Apr 7 17:47:37 xenserver1 kernel: scsi 0:0:3:0: Direct-Access Intel Multi-Flex 0308 PQ: 0 ANSI: 5
Apr 7 17:47:37 xenserver1 kernel: scsi 0:0:3:0: mptscsih: ioc0: qdepth=64, tagged=1, simple=1, ordered=0, scsi_level=6, cmd_que=1
Apr 7 17:47:37 xenserver1 kernel: scsi 0:0:3:0: alua: supports explicit TPGS
Apr 7 17:47:37 xenserver1 kernel: scsi 0:0:3:0: alua: port group 01 rel port 06
Apr 7 17:47:37 xenserver1 kernel: scsi 0:0:3:0: alua: port group 01 state S supports touSnA
Apr 7 17:47:37 xenserver1 kernel: sd 0:0:3:0: Attached scsi generic sg1 type 0
Apr 7 17:47:37 xenserver1 kernel: sd 0:0:3:0: [sdb] 209715200 512-byte logical blocks: (107 GB/100 GiB)
Apr 7 17:47:37 xenserver1 kernel: sd 0:0:3:0: [sdb] Write Protect is off
Apr 7 17:47:37 xenserver1 kernel: sd 0:0:3:0: [sdb] Write cache: enabled, read cache: enabled, supports DPO and FUA
Apr 7 17:47:37 xenserver1 kernel: sdb:
Apr 7 17:47:37 xenserver1 kernel: ldm_validate_partition_table(): Disk read failed.
Apr 7 17:47:37 xenserver1 kernel: unable to read partition table
Apr 7 17:47:37 xenserver1 kernel: sd 0:0:3:0: [sdb] Attached SCSI disk
Apr 7 17:47:39 xenserver1 multipathd: sdb: add path (operator)
Apr 7 17:47:39 xenserver1 multipathd: 22202000155fdb615: load table [0 209715200 multipath 1 queue_if_no_path 1 alua 2 1 round-robin 0 1 1 8:0 100 round-robin 0 1 1
Apr 7 17:47:39 xenserver1 multipathd: Path event for 22202000155fdb615, calling mpathcount
Apr 7 17:47:53 xenserver1 kernel: sd 0:0:0:0: alua: port group 00 state A supports touSnA

Multipath state:

22202000155fdb615 dm-0 Intel,Multi-Flex
[size=100G][features=1 queue_if_no_path][hwhandler=1 alua][rw]
\_ round-robin 0 [prio=50][active]
\_ 0:0:0:0 sda 8:0 [active][ready]
\_ round-robin 0 [prio=1][enabled]
\_ 0:0:3:0 sdb 8:16 [active][ready]

 

Pull out SCM1 for the first time

 

Messages:

Apr 7 17:52:54 xenserver1 multipathd: sda3: remove path (operator)
Apr 7 17:52:54 xenserver1 multipathd: sda3: spurious uevent, path not in pathvec
Apr 7 17:52:54 xenserver1 multipathd: sda2: remove path (operator)
Apr 7 17:52:54 xenserver1 multipathd: sda2: spurious uevent, path not in pathvec
Apr 7 17:52:54 xenserver1 multipathd: sda1: remove path (operator)
Apr 7 17:52:54 xenserver1 multipathd: sda1: spurious uevent, path not in pathvec
Apr 7 17:52:54 xenserver1 kernel: sd 0:0:0:0: [sda] Synchronizing SCSI cache
Apr 7 17:52:54 xenserver1 kernel: sd 0:0:0:0: [sda] Result: hostbyte=DID_NO_CONNECT driverbyte=DRIVER_OK
Apr 7 17:52:54 xenserver1 kernel: mptsas: ioc0: delete expander: num_phys 25, sas_addr (0x5001e671d12252ff)
Apr 7 17:52:55 xenserver1 kernel: mptbase: ioc0: LogInfo(0x31140000): Originator={PL}, Code={IO Executed}, SubCode(0x0000)
Apr 7 17:52:55 xenserver1 kernel: mptscsih: ioc0: ERROR – Received a mf that was already freed
Apr 7 17:52:55 xenserver1 kernel: mptscsih: ioc0: ERROR – req_idx=beaf req_idx_MR=6d mf=ec985e80 mr=ec9817c0 sc=(null)
Apr 7 17:52:55 xenserver1 multipathd: sda: remove path (operator)
Apr 7 17:52:55 xenserver1 multipathd: 22202000155fdb615: load table [0 209715200 multipath 1 queue_if_no_path 1 alua 1 1 round-robin 0 1 1 8:16 100]
Apr 7 17:52:55 xenserver1 multipathd: Path event for 22202000155fdb615, calling mpathcount
Apr 7 17:52:56 xenserver1 kernel: sd 0:0:3:0: alua: port group 01 state S supports touSnA
Apr 7 17:52:56 xenserver1 kernel: sd 0:0:3:0: alua: port group 01 switched to state A

Multipath state:

22202000155fdb615 dm-0 Intel,Multi-Flex
[size=100G][features=1 queue_if_no_path][hwhandler=1 alua][rw]
\_ round-robin 0 [prio=1][active]
\_ 0:0:3:0 sdb 8:16 [active][ready]

Push back SCM1 for the first time

 

Messages:
Apr 7 18:03:40 xenserver1 kernel: mptsas: ioc0: add expander: num_phys 25, sas_addr (0x5001e671d12252ff)
Apr 7 18:03:41 xenserver1 kernel: mptsas: ioc0: attaching ssp device: fw_channel 0, fw_id 0, phy 11, sas_addr 0x500015500002040a
Apr 7 18:03:41 xenserver1 kernel: target0:0:4: mptsas: ioc0: add device: fw_channel 0, fw_id 0, phy 11, sas_addr 0x500015500002040a
Apr 7 18:03:41 xenserver1 kernel: scsi 0:0:4:0: Direct-Access Intel Multi-Flex 0308 PQ: 0 ANSI: 5
Apr 7 18:03:41 xenserver1 kernel: scsi 0:0:4:0: mptscsih: ioc0: qdepth=64, tagged=1, simple=1, ordered=0, scsi_level=6, cmd_que=1
Apr 7 18:03:41 xenserver1 kernel: scsi 0:0:4:0: alua: supports explicit TPGS
Apr 7 18:03:41 xenserver1 kernel: scsi 0:0:4:0: alua: port group 00 rel port 03
Apr 7 18:03:41 xenserver1 kernel: scsi 0:0:4:0: alua: port group 00 state S supports touSnA
Apr 7 18:03:41 xenserver1 kernel: sd 0:0:4:0: Attached scsi generic sg0 type 0
Apr 7 18:03:41 xenserver1 kernel: sd 0:0:4:0: [sda] 209715200 512-byte logical blocks: (107 GB/100 GiB)
Apr 7 18:03:41 xenserver1 kernel: sd 0:0:4:0: [sda] Write Protect is off
Apr 7 18:03:41 xenserver1 kernel: sd 0:0:4:0: [sda] Write cache: enabled, read cache: enabled, supports DPO and FUA
Apr 7 18:03:41 xenserver1 kernel: sda:
Apr 7 18:03:41 xenserver1 kernel: ldm_validate_partition_table(): Disk read failed.
Apr 7 18:03:41 xenserver1 kernel: unable to read partition table
Apr 7 18:03:41 xenserver1 kernel: sd 0:0:4:0: [sda] Attached SCSI disk
Apr 7 18:03:43 xenserver1 multipathd: sda: add path (operator)
Apr 7 18:03:43 xenserver1 multipathd: 22202000155fdb615: load table [0 209715200 multipath 1 queue_if_no_path 1 alua 2 1 round-robin 0 1 1 8:0 100 round-robin 0 1 1
Apr 7 18:03:43 xenserver1 multipathd: Path event for 22202000155fdb615, calling mpathcount
Apr 7 18:03:57 xenserver1 kernel: sd 0:0:4:0: alua: port group 00 state S supports touSnA
Apr 7 18:03:57 xenserver1 kernel: sd 0:0:4:0: alua: port group 00 switched to state A

Multipath state:

22202000155fdb615 dm-0 Intel,Multi-Flex
[size=100G][features=1 queue_if_no_path][hwhandler=1 alua][rw]
\_ round-robin 0 [prio=50][active]
\_ 0:0:4:0 sda 8:0 [active][ready]
\_ round-robin 0 [prio=1][enabled]
\_ 0:0:3:0 sdb 8:16 [active][ready]

Pull out SCM1 for the second time

 

Messages:

Apr 7 18:09:31 xenserver1 kernel: sd 0:0:4:0: [sda] Synchronizing SCSI cache
Apr 7 18:09:31 xenserver1 kernel: sd 0:0:4:0: [sda] Result: hostbyte=DID_NO_CONNECT driverbyte=DRIVER_OK
Apr 7 18:09:31 xenserver1 kernel: mptsas: ioc0: delete expander: num_phys 25, sas_addr (0x5001e671d12252ff)
Apr 7 18:09:31 xenserver1 multipathd: sda: remove path (operator)
Apr 7 18:09:31 xenserver1 multipathd: 22202000155fdb615: load table [0 209715200 multipath 1 queue_if_no_path 1 alua 1 1 round-robin 0 1 1 8:16 100]
Apr 7 18:09:31 xenserver1 multipathd: Path event for 22202000155fdb615, calling mpathcount
Apr 7 18:09:37 xenserver1 kernel: sd 0:0:3:0: alua: port group 01 state A supports touSnA

Multipath state:

22202000155fdb615 dm-0 Intel,Multi-Flex
[size=100G][features=1 queue_if_no_path][hwhandler=1 alua][rw]
\_ round-robin 0 [prio=1][active]
\_ 0:0:3:0 sdb 8:16 [active][ready]

 

Push back SCM1 for the second time

 

Messages:

Apr 7 18:17:55 xenserver1 kernel: mptsas: ioc0: add expander: num_phys 25, sas_addr (0x5001e671d12252ff)
Apr 7 18:17:57 xenserver1 kernel: mptsas: ioc0: attaching ssp device: fw_channel 0, fw_id 0, phy 11, sas_addr 0x500015500002040a
Apr 7 18:17:57 xenserver1 kernel: target0:0:5: mptsas: ioc0: add device: fw_channel 0, fw_id 0, phy 11, sas_addr 0x500015500002040a
Apr 7 18:17:57 xenserver1 kernel: scsi 0:0:5:0: Direct-Access Intel Multi-Flex 0308 PQ: 0 ANSI: 5
Apr 7 18:17:57 xenserver1 kernel: scsi 0:0:5:0: mptscsih: ioc0: qdepth=64, tagged=1, simple=1, ordered=0, scsi_level=6, cmd_que=1
Apr 7 18:17:57 xenserver1 kernel: scsi 0:0:5:0: alua: supports explicit TPGS
Apr 7 18:17:57 xenserver1 kernel: scsi 0:0:5:0: alua: port group 00 rel port 03
Apr 7 18:17:57 xenserver1 kernel: scsi 0:0:5:0: alua: port group 00 state S supports touSnA
Apr 7 18:17:57 xenserver1 kernel: sd 0:0:5:0: Attached scsi generic sg0 type 0
Apr 7 18:17:57 xenserver1 kernel: sd 0:0:5:0: [sda] 209715200 512-byte logical blocks: (107 GB/100 GiB)
Apr 7 18:17:57 xenserver1 kernel: sd 0:0:5:0: [sda] Write Protect is off
Apr 7 18:17:57 xenserver1 kernel: sd 0:0:5:0: [sda] Write cache: enabled, read cache: enabled, supports DPO and FUA
Apr 7 18:17:57 xenserver1 kernel: sda:
Apr 7 18:17:57 xenserver1 kernel: ldm_validate_partition_table(): Disk read failed.
Apr 7 18:17:57 xenserver1 kernel: unable to read partition table
Apr 7 18:17:57 xenserver1 kernel: sd 0:0:5:0: [sda] Attached SCSI disk
Apr 7 18:17:58 xenserver1 multipathd: sda: add path (operator)
Apr 7 18:17:58 xenserver1 multipathd: 22202000155fdb615: load table [0 209715200 multipath 1 queue_if_no_path 1 alua 2 1 round-robin 0 1 1 8:0 100 round-robin 0 1 1
Apr 7 18:17:58 xenserver1 multipathd: Path event for 22202000155fdb615, calling mpathcount
Apr 7 18:18:06 xenserver1 kernel: sd 0:0:5:0: alua: port group 00 state S supports touSnA
Apr 7 18:18:06 xenserver1 kernel: sd 0:0:5:0: alua: port group 00 switched to state A

Multipath state:

22202000155fdb615 dm-0 Intel,Multi-Flex
[size=100G][features=1 queue_if_no_path][hwhandler=1 alua][rw]
\_ round-robin 0 [prio=50][active]
\_ 0:0:5:0 sda 8:0 [active][ready]
\_ round-robin 0 [prio=1][enabled]
\_ 0:0:3:0 sdb 8:16 [active][ready]