Sun StorageTek RDAC Multipath Failover Driver Installation Guide for Linux OS

The Sun StorageTek Redundant Dual Active Controller (RDAC) failover drivers support the following Linux OS distributions for the 2.6 kernel:

• SuSE SLES 10 SP1 and SLES 9 (x86, x86_64, IA64)
• SuSE Linux Enterprise Server 10 SP1 and 9 for IBM eServer pSeries
• Architectures (ppc64)
• Red Hat RHEL 5 (x86, x86_64, IA64)
• Red Hat Advanced Server 4 (x86, x86_64, IA64)

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About RDAC Multipath Drivers

Redundant Dual Active Controller (RDAC) is the failover driver for the Sun Storage 6180 array, StorageTek 6000 array series (includes Sun Storage 6580 and 6780 arrays) and Sun StorageTek 2500 array series. The RDAC failover driver includes these features:

• On-the-fly path validation.
• Cluster support.
• Automatic detection of path failure. The RDAC failover driver automatically routes I/O to another path in the same controller or to an alternate controller, in case all paths to a particular controller fail.
• Improved I/O retries. The RDAC driver handles vendor-specific SCSI error codes from the array controllers.
• Automatic rebalancing. When the failed controller obtains optimal status, storage array rebalance is performed automatically without user intervention.

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Prerequisites

Before you install the RDAC driver, be sure the following requirements are met:

1. The HBAs connected to the host on which you are installing the RDAC driver are supported. The driver supports QLogic, LSI, and Emulex HBAs. (For supported HBA model numbers, see the README file included in the RDAC driver package, as described in Downloading the RDAC Driver.)

2. The compiler and kernel source for the appropriate OS are installed.

3. The HBAs connected to a single storage array are the same model. Use your HBA utilities, such as HBAanywhere (Emulex) or scli (QLogic) to ensure that your storage area network (SAN) is configured properly for this requirement.

4. The base HBA driver is installed and built. The following base and host drivers are supported:

5. To verify the driver is installed, use the following command:

lsmod | grep <driver_name> 

The following sample output shows QLogic drivers (in bold text):

Module                  Size  Used by
.
.
.iscsi_tcp              56641  0
libiscsi               59329  2 ib_iser,iscsi_tcp
scsi_transport_iscsi    63569  4 ib_iser,iscsi_tcp,libiscsi
dm_mirror              61121  0 
.
usb_storage           116257  0 
qla2xxx              1007660  0
intermodule            37508  2 qla2xxx_conf,qla2xxx
lpfc                  222068  2
scsi_transport_fc      73161  1 lpfc
mptsas                 59857  3
mptbase                87649  2 mptsas,mptscsih
scsi_transport_sas     64833  1 mptsas
.
.

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Downloading the RDAC Driver

The Linux OS RDAC driver is available for the following storage products:

• Sun Storage 6180 array
• Sun Storage 6580 and 6780 arrays
• Sun StorageTek 6000 array series
• Sun StorageTek 2500 array series

The Linux OS RDAC driver is compatible with array controller firmware version 06.19.25.16 (minimum). Array firmware is bundled with Sun StorageTek Common Array Manager (CAM) and is also available at the Sun Download Center (see the URL in Step 1 of the following procedure).

RDAC drivers are available from the Sun Download Center.

Caution - MPIO and RDAC cannot coexist on the same Linux host server.

1. To download the RDAC driver, go to:

http://www.sun.com/download/index.jsp?tab=2#S

2. Select the package for the Linux OS platform.

3. Place the download in a non-volatile location on the system to be installed.

4. Load the standard HBA non-failover driver.

5. On the SuSE operating system, check the base HBA drivers are included in INITRD_MODULES in /etc/sysconfig/kernel for one of the following HBAs:

6. Make sure the kernel source tree is installed for the kernel version to be built against.

---

Installing the RDAC Driver

The following procedure describes how to install the RDAC driver for Red Hat RHEL 5, Red Hat Advanced Server 4, and Red Hat SuSE.

• Red Hat RHEL 5 package: rdac-LINUX-09.03.0B05.0042-source.tar.gz
• Red Hat Advanced Server 4 package: rdac-LINUX-09.03.0C02.0042-source.tar.gz

1. Unpack the source code using the tar command:

# tar -zxvf rdac-LINUX-xx.xx.xxxx.xxxx-source.tar.gz 

where xx.xx.xxxx.xxxx is the RDAC version you downloaded.

The files are copied to the linuxrdac-xx.xx.xx.xx directory.

2. Change to the directory containing the unpacked files. For example,

# cd linuxrdac-09.03.C2.13

3. Remove any earlier version drivers that are in this directory by running the make clean command:

# make clean -r
make V=0 -C/lib/modules/2.6.18-8.el5xen/build  M=/PTS/linuxrdac-09.03.C2.13 MODVERDIR=/lib/modules/2.6.18-8.el5xen/build/.tmp_versions SUBDIRS=/PTS/linuxrdac-09.03.C2.13 clean
make[1]: Entering directory ‘/usr/src/kernels/2.6.18-8.el5-xen-x86_64’
make[1]: Leaving directory ‘/usr/src/kernels/2.6.18-8.el5-xen-x86_64’
rm -f ./mpp_linux_sys_headers/mppLnx26p_spinlock.h mppLnx_Spinlock_Size
rm -f Module.symvers
rm -f mppUtil
rm -f genuniqueid
#

4. Compile all driver modules and utilities by running the make command:

# make
make V=0 -C/lib/modules/2.6.18-8.el5xen/build  M=/PTS/linuxrdac-09.03.C2.13 MODVERDIR=/lib/modules/2.6.18-8.el5xen/build/.tmp_versions SUBDIRS=/PTS/linuxrdac-09.03.C2.13 modules
make[1]: Entering directory ‘/usr/src/kernels/2.6.18-8.el5-xen-x86_64’
     CC [M]  /PTS/linuxrdac-09.03.C2.13/MPP_hba.o
     CC [M]  /PTS/linuxrdac-09.03.C2.13/mppLnx26p_upper.o
     CC [M]  /PTS/linuxrdac-09.03.C2.13/mppLnx26p_sysdep.o
     CC [M]  /PTS/linuxrdac-09.03.C2.13/mppCmn_s2tos3.o
     CC [M]  /PTS/linuxrdac-09.03.C2.13/mppCmn_SysInterface.o
     CC [M]  /PTS/linuxrdac-09.03.C2.13/mppLnx26p_vhbamisc.o
     CC [M]  /PTS/linuxrdac-09.03.C2.13/mppLnx26p_vhbatask.o
     CC [M]  /PTS/linuxrdac-09.03.C2.13/mppLnx26p_vhba.o
     CC [M]  /PTS/linuxrdac-09.03.C2.13/mppLnx26p_vhbaproc.o
     CC [M]  /PTS/linuxrdac-09.03.C2.13/mppLnx26p_vhbalib.o
     CC [M]  /PTS/linuxrdac-09.03.C2.13/mppLnx26p_vhbaio.o
     LD [M]  /PTS/linuxrdac-09.03.C2.13/mppUpper.o
     LD [M]  /PTS/linuxrdac-09.03.C2.13/mppVhba.o
     Building modules, stage 2.
     MODPOST
     CC      /PTS/linuxrdac-09.03.C2.13/mppUpper.mod.o
     LD [M]  /PTS/linuxrdac-09.03.C2.13/mppUpper.ko
     CC      /PTS/linuxrdac-09.03.C2.13/mppVhba.mod.o
     LD [M]  /PTS/linuxrdac-09.03.C2.13/mppVhba.ko 
make[1]: Leaving directory ‘/usr/src/kernels/2.6.18-8.el5-xen-x86_64’
make V=0 -C/lib/modules/2.6.18-8.el5xen/build  M=/PTS/linuxrdac-09.03.C2.13 MODVERDIR=/lib/modules/2.6.18-8.el5xen/build/.tmp_versions SUBDIRS=/PTS/linuxrdac-09.03.C2.13 modules
make[1]: Entering directory ‘/usr/src/kernels/2.6.18-8.el5-xen-x86_64’
     Building modules, stage 2.
     MODPOST
make[1]: Leaving directory ‘/usr/src/kernels/2.6.18-8.el5-xen-x86_64’
     gcc -D__KERNEL__   -I/lib/modules/2.6.18-8.el5xen/build/include mppLnx26p_spinlock_size.c -o mppLnx_Spinlock_Size

Sample output continued from previous page

gcc  -I/PTS/linuxrdac-09.03.C2.13 -I/PTS/linuxrdac-09.03.C2.13/mpp_linux_headers/ -I/PTS/linuxrdac-09.03.C2.13/mpp_linux_sys_headers/ -c ./utility/mppUtil.c  -o mppUtil.o
     /bin/bash ./genfileattributes bld
     gcc  -I/PTS/linuxrdac-09.03.C2.13 -I/PTS/linuxrdac-09.03.C2.13/mpp_linux_headers/ -I/PTS/linuxrdac-09.03.C2.13/mpp_linux_sys_headers/ -c ./utility/mppUtil26p_sysdep.c -o mppUtilSysdep.o
     gcc mppUtil.o mppUtilSysdep.o -o mppUtil
     gcc -o genuniqueid genuniqueid.c

5. Uninstall any existing RDAC drivers using the make uninstall command:

# make uninstall
   MPP driver is currently not installed on the system
   [root@va64-x4100d-sca11 linuxrdac-09.03.C2.13]

6. Install the new RDAC driver using the make install command. This command:

• Copies the driver modules to the kernel module tree.
• Builds the new RAMdisk image (mpp-‘uname -r‘.img) which includes the RDAC driver modules and all driver modules that are needed at boot time.


# make install make V=0 -C/lib/modules/2.6.18-8.el5xen/build M=/PTS/linuxrdac-09.03.C2.13 MODVERDIR=/lib/modules/2.6.18-8.el5xen/build/.tmp_versions SUBDIRS=/PTS/linuxrdac-09.03.C2.13 modules make[1]: Entering directory ‘/usr/src/kernels/2.6.18-8.el5-xen-x86_64’ Building modules, stage 2. MODPOST make[1]: Leaving directory ‘/usr/src/kernels/2.6.18-8.el5-xen-x86_64’ make V=0 -C/lib/modules/2.6.18-8.el5xen/build M=/PTS/linuxrdac-09.03.C2.13 MODVERDIR=/lib/modules/2.6.18-8.el5xen/build/.tmp_versions SUBDIRS=/PTS/linuxrdac-09.03.C2.13 modules make[1]: Entering directory ‘/usr/src/kernels/2.6.18-8.el5-xen-x86_64’ Building modules, stage 2. MODPOST make[1]: Leaving directory ‘/usr/src/kernels/2.6.18-8.el5-xen-x86_64’ /bin/bash ./genfileattributes bld gcc -I/PTS/linuxrdac-09.03.C2.13 -I/PTS/linuxrdac-09.03.C2.13/mpp_linux_headers/ -I/PTS/linuxrdac-09.03.C2.13/mpp_linux_sys_headers/ -c ./utility/mppUtil26p_sysdep.c -o mppUtilSysdep.o gcc mppUtil.o mppUtilSysdep.o -o mppUtil Checking Host Adapter Configuration... Unsupported Host Adapter Model: Product ID fc10(rev01) Unsupported Host Adapter Model: Product ID fc10(rev01) Detected 2 Emulex Host Adapter Port(s) on the system Detected 1 LSI Host Adapter Port(s) on the system Detected 2 QLogic Host Adapter Port(s) on the system Host Adapters from different supported vendors co-exists on your system. Unsupported model from Vendor Emulex exists. Please make sure that only one supported model of HBA is connected to Storage Array.

7. Type yes when you are prompted to continue:

 Do you want to continue (yes or no) ? yes
    Please wait while we modify the system configuration files.
    Your kernel version is 2.6.18-8.el5xen
    Preparing to install MPP driver against this kernel version...
    Generating module dependencies...
    Warning: Duplicate module options detected.
         Option in /etc/modprobe.conf ( max_luns=256 ) takes precedence over MPP default setting ( max_luns=512 ).
Creating new MPP initrd image...
        You must now edit your boot loader configuration file, /boot/grub/menu.lst, to
        add a new boot menu, which uses mpp-2.6.18-8.el5xen.img as the initrd image.
        Now Reboot the system for MPP to take effect.
        The new boot menu entry should look something like this (note that it may
        vary with different system configuration):
 
        ...
 
                title Red Hat Linux (2.6.18-8.el5xen) with MPP support
                root (hd0,5)
                kernel /vmlinuz-2.6.18-8.el5xen ro root=LABEL=RH9
                initrd /mpp-2.6.18-8.el5xen.img
        ...
   MPP driver package has been successfully installed on your system.

8. Follow the on-screen instructions to modify the grub.conf file. Change the module and initrd names as follows:

The content of the grub.conf file looks similar to the following. (The revised module and initrd names are shown in bold text.)

# boot=/dev/sda
	default=0
	timeout=5
	title Red Hat Enterprise Linux Server (2.6.18-8.el5xen)
        	root (hd0,0)
        	kernel /xen.gz-2.6.18-8.el5 com1=9600n8
        	module /vmlinuz-2.6.18-8.el5xen ro root=LABEL=/ console=ttyS0,9600n8 rhgb quiet
	module /mpp-2.6.18-8.el5xen.img 
	title Red Hat Enterprise Linux Server-base (2.6.18-8.el5)
        	root (hd0,0)
        	kernel /vmlinuz-2.6.18-8.el5 ro root=LABEL=/ console=ttyS0,9600n8 rhgb quiet
	initrd /mpp-2.6.18-8.el5xen.img 

9. Reboot the Linux server.

# reboot

10. After the server is rebooted, log in and verify the driver stack is properly loaded using the lsmod command. The driver stack for Red Hat and SuSE platforms are as follows:

• Red Hat platforms--scsi_mod, sd_mod, sg, mppUpper, mppVhba, and base level HBA drivers (for example, qla2xxx, qla2300) are loaded.
• SuSE platforms--sg, mppUpper, mppVhba, and base level HBA drivers (for example, qla2xxx, qla2300) are loaded.


# modinfo qla2xxx filename: /lib/modules/2.6.18-8.el5xen/kernel/drivers/scsi/qla2xxx/qla2xxx.ko version: 8.02.08 license: GPL description: QLogic Fibre Channel HBA Driver author: QLogic Corporation srcversion: F368B42790B83A8F18E4151 alias: pci:v00001077d00002532sv*sd*bc*sc*i*

# modinfo lpfc
   filename:       /lib/modules/2.6.18-8.el5xen/kernel/drivers/scsi/lpfc/lpfc.ko
   version:        0:8.1.10.12
   author:         Emulex Corporation - tech.support@emulex.com
   description:    Emulex LightPulse Fibre Channel SCSI driver 8.1.10.12
   license:        GPL
   srcversion:     13F4CC10783BE62B7822C3B

11. Verify the content of the modprobe.conf.mppappend file:

# more /opt/mpp/modprobe.conf.mppappend
    ### BEGIN OF MPP Driver Changes ###
    options scsi_mod  max_report_luns=256 max_luns=256
    alias scsi_hostadapter99 mppVhba
    alias scsi_hostadapter98 mptsas
    options qla2xxx ql2xfailover=0 ql2xretrycount=3 ql2xprocessnotready=0 qlport_down_retry=35
    alias scsi_hostadapter96 qla2xxx
    options lpfc lpfc_nodev_tmo=60
    alias scsi_hostadapter97 lpfc
    ## END OF MPP Driver Changes ###

12. Verify the RDAC driver discovered the available physical LUNs and created virtual LUNs by typing the following command:

#  ls -lR /proc/mpp
    /proc/mpp:
    total 0

13. Verify all drivers are running.

# lsmod | grep qla
qla2xxx            1007660  0
intermodule       37508    1  qla2xxx
scsi_mod       184057    16 ib_iser,iscsi_tcp, libiscsi,scsi_transport_iscsi,sr_mod,mppVhba,lpfc, scsi_transport_fc,qla2xxx,usb_storage,mptsas,mptscsih,scsi_transport_sas,mppUpper,sg,sd_mod

# modinfo lpfc | grep version
       version:        0:8.0.16.6_p3 37504CE1A0639D7C3FD1BAB 

14. Verify RDAC is configured with the MPP drivers.

# more /etc/modprobe.conf
    alias eth0 e1000
    alias eth1 e1000
    alias eth2 e1000
    alias eth3 e1000
    alias scsi_hostadapter mptbase
    alias scsi_hostadapter1 mptsas
    alias scsi_hostadapter2 lpfc
    alias scsi_hostadapter3 qla2xxx
    alias scsi_hostadapter4 usb-storage
    install qla2xxx /sbin/modprobe qla2xxx_conf; /sbin/modprobe --ignore-install qla2xxx
    remove qla2xxx /sbin/modprobe -r --first-time --ignore-remove qla2xxx && { /sbin/modprobe -r --ignore-remove qla2xxx_conf; }
    alias qla2100 qla2xxx
    alias qla2200 qla2xxx
    alias qla2300 qla2xxx
    alias qla2322 qla2xxx
    alias qla2400 qla2xxx
    options scsi_mod max_luns=256
    alias scsi_hostadapter5 lpfc
    ### BEGIN MPP Driver Comments ###
    remove mppUpper if [ ‘ls -a /proc/mpp | wc -l‘ -gt 2 ]; then echo -e "Please Unload Physical HBA Driver prior to unloading mppUpper."; else /sbin/modprobe -r --ignore-remove mppUpper; fi
    # Additional config info can be found in /opt/mpp/modprobe.conf.mppappend.
    # The Above config info is needed if you want to make mkinitrd manually.
    # Please read the Readme file that came with MPP driver for building RamDisk manually.
    # Edit the ’/etc/modprobe.conf’ file and run ’mppUpdate’ to create Ramdisk dynamically.
    ### END MPP Driver Comments ###

15. Verify the disk devices are mapped from the array to the host, as follows:

• Check the array mappings in Common Array Manager, to ensure that you have mapped a volume on the array to the Linux host.
• Use the /usr/sbin/mppUtil -a <array_name_in_CAM> command to get a report on how many devices can be seen by the MPP driver (see Multipath Failover Driver Utilities).
• View the /proc/scsi/mpp file for array devices.
• View /proc/scsi/<base_hba_driver_name>/[0-9|a-z], for information about what devices can be seen.

See TABLE 1 for a list of HBA base driver names. The files in this directory are labeled 0 through 9 or A through Z. Each file represents a port on the HBA, which includes World Wide Names of storage devices and LUNs reported.

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Multipath Failover Driver Utilities

The MPP RDAC driver installation creates three utilities for your use:

• mppUtil
• lsvdev
• mppSupport

mppUtil Utility

The mppUtil utility is a general purpose command-line driven utility that works only with MPP-based RDAC solutions. The utility instructs RDAC to perform various maintenance tasks, but you can also use the utility to troubleshoot failover problems.

To use the mppUtil utility, type this command and press enter.

mppUtil [-a target_name] [-c wwn_file_name] [-d debug_level] [-e error_level] [-g virtual_target_id] [-I host_num] [-o feature_action_name
[=value][, SaveSettings]][-s "failback" | "avt" | "busscan" | "forcerebalance"] [-S] [-U][-V]

The mppUtil utility is a cross-platform tool. Some parameters might not have a meaning in a particular operating system environment. A description of each parameter follows.

lsdev Utility

The lsdev utility provides a map of your array LUNs to their Linux block devices. To use the lsdev utility, type this command and press enter.

# /opt/mpp/lsdev

For example:

/usr/sbin # /opt/mpp/lsvdev

Array Name Lun sd device
-------------------------------------
myarray 0 -> /dev/sdf
myarray 1 -> /dev/sdg
myarray 2 -> /dev/sdh
myarray 3 -> /dev/sdi 

mppSupport Utility

The mppSupport utility provides information about your system, array connection, and configuration for Sun Services to assist you with any problems you might have.

To use the mppSupport utility, type this command and press enter.

# /opt/mppSupport

The collected support data is saved in the file:

/tmp/mppSupportdata_myhost_<RDACversion>_<dateandtime>.tar.gz

---

Linux RDAC Configuration Settings

The RDAC driver contains configuration settings that can modify the behavior of the driver. Any changes to the settings take effect on the next reboot of the host. The default values listed here are the platform-independent settings. Many of these values are overridden by the failover installer for Linux. For Linux, the configuration settings are located in the /etc/mpp.conf file.

After you change a configuration value, you must run the mppUpdate utility and reboot your Linux server for the change to take effect.

Caution - You might lose access to the storage array if you change these settings from their configured values.

Wait Time Settings

When the failover driver receives an I/O request for the first time, the failover driver logs timestamp information for the request. If a request returns an error and the failover driver decides to retry the request, the current time is compared with the original timestamp information. Depending on the error and the amount of time that has elapsed, the request is retried to the current owning controller for the LUN or a failover is performed and the request sent to the alternate controller. This process is known as a "Wait Time."

Caution - Possible loss of data access--If you change these settings from their configured values, you might lose access to the storage array.

The configuration settings can be found in the /etc/mpp.conf file.

Updating the initrd Image

1. After you change a configuration value, run the mppUpdate utility and reboot the Linux server for the change to take effect. An MPP initrd image is created, as shown in the following example:

# mppUpdate
   Unsupported Host Adapter Model: Product ID fc10(rev01)
   Unsupported Host Adapter Model: Product ID fc10(rev01)
   Detected 2 Emulex Host Adapter Port(s) on the system
   Detected 1 LSI Host Adapter Port(s) on the system
   Detected 2 QLogic Host Adapter Port(s) on the system
   Host Adapters from different supported vendors co-exists on your system.
   Unsupported model from Vendor Emulex  exists.
   Warning: Duplicate module options detected.
         Option in /etc/modprobe.conf ( max_luns=256 ) takes precedence over MPP default setting ( max_luns=512 ).
   Creating new MPP initrd image...

2. Reboot the host server:

# reboot

---

Troubleshooting Linux RDAC Drivers

How do I get logs from RDAC in the Linux OS?

Use the mppSupport command to obtain several logs related to RDAC. The mppSupport command is found in the /opt/mpp/mppSupport directory. The command creates a file named mppSupportdata_hostname_RDAC version_datetime.tar.gz in the /tmp directory.

How does persistent naming work?

The Linux OS SCSI device names can change when the host system restarts. Use a utility, such as devlabel, to create user-defined device names that will map devices based on a unique identifier. The udev method is the preferred method for SLES10 and RHEL 5.

What must I do after applying a kernel update?

After you apply the kernel update and start the new kernel, perform these steps to build the RDAC Initial Ram Disk image (initrd image) for the new kernel:

1. Change the directory to the Linux RDAC source code directory.

2. Type the following command, and press Enter.

make uninstall

3. Reinstall RDAC.

What is the Initial Ram Disk Image (initrd image), and how do I create a new initrd image?

The initrd image is automatically created when the driver is installed by using the make install command. The boot loader configuration file must have an entry for this newly created image.

The initrd image is located in the boot partition. The file is named mpp-uname -r.img.

For a driver update, if the system already has a previous entry for RDAC, the system administrator must modify the existing RDAC entry in the boot loader configuration file. In most of the cases, no change is required if the kernel version is the same.

To create a new initrd image, type the following command and press Enter.

# mppUpdate

The old image file is overwritten with the new image file.

If third-party drivers are needed to be added to the initrd image, change the /etc/sysconfig/kernel file (SuSE) with the third-party driver entries. Run the mppUpdate command again to create a new initrd image.

How can I see if volumes have been added?

Run hot_add -s or hot_add to add the newly mapped volumes.

How do I remove unmapped or disconnected devices from the existing host?

Run hot_add -d to remove all unmapped or disconnected devices.

What if I remap a LUN from the storage array?

Run hot_add -u to update the host with the changed LUN mapping.

What if I change the size of the LUN on the storage array?

Run hot_add -c to change the size of the LUN on the host.

How do I make sure that RDAC finds the available storage arrays?

To make sure that the RDAC driver has found the available storage arrays and created virtual storage arrays for them, type the following commands, and press Enter after each command.

# ls -lR /proc/mpp

# mppUtil -a

# /opt/mpp/lsvdev

To show all attached and discovered volumes, type the following command and press Enter.

# cat /proc/scsi/scsi

What must I do if I receive this message?

Caution - Changing the storage array name can cause host applications to lose access to the storage array if the host is running certain path failover drivers. If any of your hosts are running path failover drivers, please update the storage array name in your path failover driver’s configuration file before rebooting the host machine to insure uninterrupted access to the storage array. Refer to your path failover driver documentation for more details.

The path failover drivers that cause this warning are the RDAC drivers on Linux. The storage array user label is used for storage system-to-virtual target ID binding in the RDAC driver. For the Linux OS, change the following file to add the storage array user label and its virtual target ID.

# more /var/mpp/devicemapping

Determining if a Path Failed

With the failover driver, two cases determine if a path has failed:

• A path to a controller has failed, but the driver has other paths to the same controller that it can use. This situation causes a degraded condition and must be corrected before the controller can switch to an alternate path.

An entry is made in the OS system log that shows that the failover driver has detected a path failure. CAM does not generate an alarm because no internal problems exist for the array.

• All of the paths to a controller have failed, or the controller itself has failed, and the other controller is now used to service the I/O.

CAM generates the “Volume Not on Preferred Path" alarm for all volumes affected by this scenario. If the array administrator has configured notifications in CAM, the administrator will receive email from CAM or a configured SNMP server. You also have the option of opening a service request using the Auto Service Request (ASR) feature of CAM. The resultant message and alarm will provide information about the fault, along with possible recovery instructions.

Error Levels

The failover driver has five error levels for messages that are logged to the Linux OS error log:

• Fatal errors
• Controller failover events
• Path failover events
• Retry errors
• Recovered errors

Fatal Errors

TABLE 5 lists the possible Linux OS fatal driver errors.

Controller and Path Failover Events

The following items are examples of failover driver controller events and path failover events:

• Change of AVT setting detected
• Failover command issued
• AVT failover invoked
• Path failure detected

Sun StorageTek RDAC Multipath Failover Driver Installation Guide for Linux OS

820-4738-13

Copyright © 2009 Sun Microsystems, Inc. All rights reserved.