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SAN hosts and cloud clients

Use Oracle Linux 6.4 with ONTAP

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You can use the ONTAP SAN host configuration settings to configure Oracle Linux 6.4 with ONTAP as the target.

Install the Linux Unified Host Utilities

The NetApp Linux Unified Host Utilities software package is available on the NetApp Support Site in a 32-bit and 64-bit .rpm file. If you don't know which file is right for your configuration, use the NetApp Interoperability Matrix Tool to verify which one you need.

NetApp strongly recommends installing the Linux Unified Host Utilities, but it's not mandatory. The utilities don't change any settings on your Linux host. The utilities improve management and assist NetApp customer support in gathering information about your configuration.

If you have Linux Unified Host Utilities currently installed, you should either upgrade it to the latest version, or remove it and follow these steps to install the latest version.

Steps

  1. Download the 32-bit or 64-bit Linux Unified Host Utilities software package from the NetApp Support Site to your host.

  2. Install the software package:

    rpm -ivh netapp_linux_unified_host_utilities-7-1.x86_64

Note You can use the configuration settings provided in this document to configure cloud clients connected to Cloud Volumes ONTAP and Amazon FSx for ONTAP.

SAN Toolkit

The toolkit is installed automatically when you install the NetApp Host Utilities package. This kit provides the sanlun utility, which helps you manage LUNs and HBAs. The sanlun command returns information about the LUNs mapped to your host, multipathing, and information necessary to create initiator groups.

Example

In the following example, the sanlun lun show command returns LUN information.

# sanlun lun show all

Example output:

controller(7mode/E-Series)/            device     host               lun
vserver(cDOT/FlashRay)   lun-pathname  filename   adapter  protocol  size    Product
------------------------------------------------------------------------------------
data_vserver          /vol/vol1/lun1   /dev/sdb   host16   FCP       120.0g  cDOT
data_vserver          /vol/vol1/lun1   /dev/sdc   host15   FCP       120.0g  cDOT
data_vserver          /vol/vol2/lun2   /dev/sdd   host16   FCP       120.0g  cDOT
data_vserver          /vol/vol2/lun2   /dev/sde   host15   FCP       120.0g  cDOT

SAN Booting

What you'll need

If you decide to use SAN booting, it must be supported by your configuration. You can use the NetApp Interoperability Matrix Tool to verify that your OS, HBA, HBA firmware and the HBA boot BIOS, and ONTAP version are supported.

Steps

  1. Map the SAN boot LUN to the host.

  2. Verify that multiple paths are available.

    Note Multiple paths become available after the host operating system is up and running on the paths.

  3. Enable SAN booting in the server BIOS for the ports to which the SAN boot LUN is mapped.

    For information on how to enable the HBA BIOS, see your vendor-specific documentation.

  4. Reboot the host to verify that the boot was successful.

Multipathing

For Oracle Linux 6.4 the /etc/multipath.conf file must exist, but you do not need to make specific changes to the file. Oracle Linux 6.4 is compiled with all settings required to recognize and correctly manage ONTAP LUNs.
To Enable ALUA Handler, perform the following steps:

Steps

  1. Create a backup of the initrd-image.

  2. Append the following parameter value to the kernel for ALUA and non-ALUA to work:
    rdloaddriver=scsi_dh_alua

    Example
    kernel /vmlinuz-3.8.13-68.1.2.el6uek.x86_64 ro root=/dev/mapper/vg_ibmx3550m421096-lv_root rd_NO_LUKSrd_LVM_LV=vg_ibmx3550m421096/lv_root LANG=en_US.UTF-8 rd_NO_MDSYSFONT=latarcyrheb-sun16 crashkernel=256M KEYBOARDTYPE=pc KEYTABLE=us rd_LVM_LV=vg_ibmx3550m421096/lv_swap rd_NO_DM rhgb quiet rdloaddriver=scsi_dh_alua

  3. Use the mkinitrd command to recreate the initrd-image.
    Oracle 6x and later versions use either:
    The command: mkinitrd -f /boot/ initrd-"uname -r".img uname -r
    Or
    The command: dracut -f

  4. Reboot the host.

  5. Verify the output of the cat /proc/cmdline command to ensure that the setting is complete.
    You can use the multipath -ll command to verify the settings for your ONTAP LUNs.
    There should be two groups of paths with different priorities. The paths with higher priorities are Active/Optimized, which means they are serviced by the controller where the aggregate is located. The paths with lower priorities are active but are non-optimized because they are served from a different controller. The non-optimized paths are only used when optimized paths are not available.

Example

The following example displays the correct output for an ONTAP LUN with two Active/Optimized paths and two Active/non-Optimized paths:

# multipath -ll
3600a09803831347657244e527766394e dm-5 NETAPP,LUN C-Mode
size=80G features='4 queue_if_no_path pg_init_retries 50 retain_attached_hw_handle' hwhandler='1 alua' wp=rw
|-+- policy='round-robin 0' prio=50 status=active
| |- 0:0:26:37 sdje 8:384   active ready running
| |- 0:0:25:37 sdik 135:64  active ready running
|-+- policy='round-robin 0' prio=10 status=enabled
  |- 0:0:18:37 sdda 70:128  active ready running
  |- 0:0:19:37 sddu 71:192  active ready running
Note A single LUN shouldn't require more than four paths. Having more than four paths might cause path issues during storage failures.

The Oracle Linux 6.4 OS is compiled to recognize ONTAP LUNs and automatically set all configuration parameters correctly.

The multipath.conf file must exist for the multipath daemon to start. If this file doesn't exist, you can create an empty, zero-byte file by using the touch /etc/multipath.conf command.

The first time you create the multipath.conf file, you might need to enable and start the multipath services by using the following commands:

# chkconfig multipathd on
# /etc/init.d/multipathd start

There is no requirement to add devices directly to the multipath.conf file, unless you have devices that you do not want multipath to manage or you have existing settings that override defaults. To exclude the unwanted devices, you add the following syntax to the multipath.conf file, replacing <DevId> with the WWID string of the device you want to exclude:

blacklist {
        wwid <DevId>
        devnode "^(ram|raw|loop|fd|md|dm-|sr|scd|st)[0-9]*"
        devnode "^hd[a-z]"
        devnode "^cciss.*"
}
Example

In the following example, sda is the local SCSI disk that you want to add to the blacklist.

Steps

  1. Run the following command to determine the WWID:

    # /lib/udev/scsi_id -gud /dev/sda
360030057024d0730239134810c0cb833

  2. Add this WWID to the "blacklist" stanza in /etc/multipath.conf:

    blacklist {
     wwid   360030057024d0730239134810c0cb833
     devnode "^(ram|raw|loop|fd|md|dm-|sr|scd|st)[0-9]*"
     devnode "^hd[a-z]"
     devnode "^cciss.*"
}

You should always check your /etc/multipath.conf file, especially in the defaults section, for legacy settings that might be overriding default settings.

The following table demonstrates the critical multipathd parameters for ONTAP LUNs and the required values. If a host is connected to LUNs from other vendors and any of these parameters are overridden, they must be corrected by later stanzas in the multipath.conf file that apply specifically to ONTAP LUNs. Without this correction, the ONTAP LUNs might not work as expected. You should only override these defaults in consultation with NetApp, the OS vendor, or both, and only when the impact is fully understood.

Parameter Setting

detect_prio

yes

dev_loss_tmo

"infinity"

failback

immediate

fast_io_fail_tmo

5

features

"3 queue_if_no_path pg_init_retries 50"

flush_on_last_del

"yes"

hardware_handler

"0"

no_path_retry

queue

path_checker

"tur"

path_grouping_policy

"group_by_prio"

path_selector

"round-robin 0"

polling_interval

5

prio

"ontap"

product

LUN.*

retain_attached_hw_handler

yes

rr_weight

"uniform"

user_friendly_names

no

vendor

NETAPP
Example

The following example shows how to correct an overridden default. In this case, the multipath.conf file defines values for path_checker and detect_prio that are not compatible with ONTAP LUNs.
If they cannot be removed because of other SAN arrays still attached to the host, these parameters can be corrected specifically for ONTAP LUNs with a device stanza.

defaults {
 path_checker readsector0
 detect_prio no
 }
devices {
 device {
 vendor "NETAPP "
 product "LUN.*"
 path_checker tur
 detect_prio yes
 }
}
Note To configure Oracle Linux 6.4 Red Hat Enterprise Kernel (RHCK), use the recommended settings for Red Hat Enterprise Linux (RHEL) 6.4.

Known issues

The Oracle Linux 6.4 with ONTAP release has the following known issues:

NetApp Bug ID Title Description

713555

QLogic adapter resets are seen on OL6.4 and OL5.9 with UEK2 on controller faults such as takeover/giveback, and reboot

QLogic adapter resets are seen on OL6.4 hosts with UEK2 (kernel-uek-2.6.39-400.17.1.el6uek) or OL5.9 hosts with UEK2 (kernel-uek-2.6.39 400.17.1.el5uek) when controller faults happen (such as takeover, giveback, and reboots). These resets are intermittent. When these adapter resets happen, a prolonged I/O outage (sometimes, more than 10 minutes) might occur until the adapter resets succeed and the paths' status are updated by dm-multipath.

In /var/log/messages, messages similar to the following are seen when this bug
is hit:
kernel: qla2xxx [0000:11:00.0]-8018:0: ADAPTER RESET ISSUED nexus=0:2:13.

This is observed with the kernel version:
On OL6.4: kernel-uek-2.6.39-400.17.1.el6uek
On OL5.9: kernel-uek-2.6.39-400.17.1.el5uek

715217

Delay in path recovery on OL6.4 or OL5.9 hosts with UEK2 may result in delayed I/O resumption on controller or fabric faults

When a controller fault (storage failover or giveback, reboots and so on) or a fabric fault (FC port disable or enable) occurs with I/O on Oracle Linux 6.4 or Oracle Linux 5.9 hosts with UEK2 Kernel, the path recovery by DM-Multipath takes a long time (4mins. to 10 mins).
Sometimes, during the paths recovering to active state, the following lpfc driver errors are also seen:
kernel: sd 0:0:8:3: [sdlt] Result: hostbyte=DID_ERROR driverbyte=DRIVER_OK

Due to this delay in path recovery during fault events, the I/O resumption also delays.

OL 6.4 Versions:
device-mapper-1.02.77-9.el6
device-mapper-multipath-0.4.9-64.0.1.el6
kernel-uek-2.6.39-400.17.1.el6uek

OL 5.9 Versions:
device-mapper-1.02.77-9.el5
device-mapper-multipath-0.4.9-64.0.1.el5
kernel-uek-2.6.39-400.17.1.el5uek

709911

DM Multipath on OL6.4 & OL5.9 iSCSI with UEK2 kernel takes long time to update LUN path status after storage faults

On systems running Oracle Linux 6 Update4 and Oracle Linux 5 Update9 iSCSI with Unbreakable Enterprise Kernel Release 2 (UEK2), a problem has been seen during storage fault events where DM Multipath (DMMP) takes around 15 minutes to update the path status of Device Mapper (DM) devices (LUNs).
If you run the "multipath -ll" command during this interval, the path status is shown as "failed ready running" for that DM device (LUN). The path status is eventually updated as "active ready running."
This issue is seen with following version:
Oracle Linux 6 Update 4:
UEK2 Kernel: 2.6.39-400.17.1.el6uek.x86_64
Multipath: device-mapper-multipath-0.4.9-64.0.1.el6.x86_64
iSCSI: iscsi-initiator-utils-6.2.0.873-2.0.1.el6.x86_64

Oracle Linux 5 Update 9:
UEK2 Kernel: 2.6.39-400.17.1.el5uek
Multipath: device-mapper-multipath-0.4.9-64.0.1.el5.x86_64
iSCSI: iscsi-initiator-utils-6.2.0.872-16.0.1.el5.x86_64

739909

The SG_IO ioctl system call fails on dm-multipath devices after an FC fault on OL6.x and OL5.x hosts with UEK2

A problem is seen on Oracle Linux 6.x hosts with UEK2 kernel and Oracle Linux 5.x hosts with UEK2 kernel. The sg_* commands on a multipath device fail with EAGAIN error code (errno) after a fabric fault that makes all the paths in the active path group go down. This problem is seen only when there is no I/O occurring to the multipath devices.
The following is an example:

# sg_inq -v /dev/mapper/3600a098041764937303f436c75324370
inquiry cdb: 12 00 00 00 24 00
ioctl(SG_IO v3) failed with os_err (errno) = 11
inquiry: pass through os error: Resource temporarily unavailable
HDIO_GET_IDENTITY ioctl failed:
Resource temporarily unavailable [11]
Both SCSI INQUIRY and fetching ATA information failed on /dev/mapper/3600a098041764937303f436c75324370
#

This problem occurs because the path group switchover to other active groups is not activated during ioctl() calls when no I/O is occurring on the DM-Multipath device. The problem has been observed on the following versions of the kernel-uek and device-mapper-multipath packages:

OL6.4 versions:
kernel-uek-2.6.39-400.17.1.el6uek
device-mapper-multipath-0.4.9-64.0.1.el6

OL5.9 versions:
kernel-uek-2.6.39-400.17.1.el5uek
device-mapper-multipath-0.4.9-64.0.1.el5
Note For Oracle Linux (Red Hat compatible kernel) known issues, see the known issues for Red Hat Enterprise Linux (RHEL) 6.4.