Storage Fusion Architecture Multipath (v1.
Table of Contents ............................................................................................................................ 2 1. OVERVIEW ................................................................................................................................ 3 2. DDN MULTIPATH RPM VERSIONS ............................................................................................ 3 3. INSTALLATION ...................................................................................
1. OVERVIEW This document provides instructions on how to install DDN’s multipath RPM and manage Linux multipathing on DDN’s family of Disk Arrays. The ddn_mpath_RHEL5_SLES10-1.1-0.x86_64.rpm provides validated and optimized configuration settings to achieve load balancing, path failover, and controller failover of DDN disk arrays in supported Linux environments. DDN’s multipath ddn_mpath_RHEL5_SLES10-1.1-0.x86_64.
3. INSTALLATION 3.1 RPM INSTALLATION Determine the Linux distribution on the host and cross-reference with the version listed in the table in section 2.0. Apply the RPM installation steps for the specific Linux version installed on the Linux host. 3.1.1 DETERMINING THE LINUX DISTRIBUTION AND VERSION Determing the distribution source can be done by running the Linux shell command: cat /etc/issue For example: #cat /etc/issue Welcome to SUSE Linux Enterprise Server 11 SP1 (x86_64) - Kernel \r (\l).
3.1.2 RPM INSTALLATION ON RHEL 5.4 – RHEL 5.6 AND SLES 10 SP2 For Red Hat Enterprise Linux 5, update 4,5 and 6, and for SuSE Enterprise Linux Server 10 SP2, run the command shown in the example below: # rpm -ivh ddn_mpath_RHEL5_SLES10-1.1-0.x86_64.rpm Preparing... ########################################### [100%] 1:ddn_mpath_RHEL5_SLES10 ########################################### [100%] The DDN mpath config file has been installed as /etc/multipath.conf.ddn. Rename this file to /etc/multipath.
Step 2: # rpm -ivh ddn_mpath_SLES11-1.1-0.x86_64.rpm Preparing... ########################################### [100%] 1:ddn_mpath_SLES11 ########################################### [100%] The DDN mpath config file has been installed as /etc/multipath.conf.ddn. Rename this file to /etc/multipath.conf if the file does not already exist. Manually merge the DDN supplied file with /etc/multipath.conf if one is already in use. Please read the DDN Multipath Manual for more information. 3.
4. ARCHITECT AND CONFIGURE YOUR DDN STORAGE ARRAY Determine the LUN mapping configuration required for each host and architect the storage layout and mapping required. Storage architecture and host connectivity implementation details are beyond the scope of this guide. Each application requirements will demand different implementations.
On S2A 9900, use the “user” and/or “zoning” directOS commands to achieve a port zoning configuration which provides access to the LUN from ports of both controllers. In the zoning example below, all four LUNs are presented on all 8 ports. Highlighted in yellow are the internal LUNs owned by the respective controllers, illustrating which S2A 9900 host ports will provide preferred access to each LUN.
In the SFAOS, host channels are referenced by Controller, Raid Processor, and Port values, and in the example below VDs 0 to 3 are presented to all hosts through all host channels. S2A 6620 models have 4 Fibre Channel Ports. The WebUI illustrates enabled host channels on which the presentations will be available: 5.
© DataDirect Networks 2011. Multipath (V1.
6. ACTIVATING MULTIPATHD multipathd is the daemon that will monitor device paths at intervals configured using the device “polling_interval” directive in the /etc/multipath.conf file. Note that device path failover is controlled by the “no_path_retry” directive in the event of a primary path failure. This component is described in detail in later sections of this document.
7. INTRODUCTION TO DM-MULTIPATH DDN’s multipath ddn_mpath_RHEL5_SLES10-0.4-7.x86_64.rpm is an extension to the linux multipath tools package: device mapper multipathing, dm-multipath. dm-multipath provides a means for accessing a device with multiple paths to that device in Linux. The device mapper kernel module creates a single SCSI block device for every LUN probed by Linux at boot time (or manually – see later in this document).
7.2 DM-MULTIPATH COMPONENTS The dm-multipath kernel module – Provides control over paths and priorities. The multipath daemon (multipathd) – Used by the Linux kernel to monitor and control the multipath paths. The multipath command – Utilized by the user to manipulate (view, flush cached entries…) multipath devices. The /etc/multipath.conf file – The configuration file read by multipathd to describe the behaviors and attributes of multipath devices.
7.4 LINUX SCSI DEVICE ENUMERATION Linux enumerates SCSI devices in order of Host:BUS:ID:LUN # lsscsi -g [0:0:0:0] [0:0:6:0] [1:0:0:0] [1:0:0:1] [1:0:0:2] [2:0:0:0] [2:0:0:1] [2:0:0:2] disk process disk disk disk disk disk disk SEAGATE PE/PV DDN DDN DDN DDN DDN DDN ST373207LC 1x2 SCSI BP S2A 6620 S2A 6620 S2A 6620 S2A 6620 S2A 6620 S2A 6620 D703 1.0 1.03 1.03 1.03 1.03 1.03 1.
# multipath -ll mpath19 (360001ff0721160000000002688e10002) dm-2 DDN,S2A 6620 [size=21T][features=1 queue_if_no_path][hwhandler=0][rw] \_ round-robin 0 [prio=50][active] \_ 1:0:0:2 sdg 8:96 [active][ready] \_ round-robin 0 [prio=10][enabled] \_ 2:0:0:2 sdf 8:80 [active][ready] [size=21T][features=1 queue_if_no_path][hwhandler=0][rw] ^ ^ ^ ^ | | | |___ Device Permissions | | |___________ Hardware Handler | |_________________________ Supported Features |________________________________________________ Size of
# multipath -ll mpath19 (360001ff0721160000000002688e10002) dm-2 DDN,S2A 6620 [size=21T][features=1 queue_if_no_path][hwhandler=0][rw] \_ round-robin 0 [prio=50][active] \_ 1:0:0:2 sdg 8:96 [active][ready] \_ round-robin 0 [prio=10][enabled] \_ 2:0:0:2 sdf 8:80 [active][ready] The previously mentioned Paths are organized into Path Groups. Only one path group can be active at any time. The Path Selector determines which path in the path group will be used to handle the next IO.
# multipath -ll mpath19 (360001ff0721160000000002688e10002) dm-2 DDN,S2A 6620 [size=21T][features=1 queue_if_no_path][hwhandler=0][rw] \_ round-robin 0 [prio=50][active] \_ 1:0:0:2 sdg 8:96 [active][ready] \_ round-robin 0 [prio=10][enabled] \_ 2:0:0:2 sdf 8:80 [active][ready] First Path on Path Group 1 (could be more than one) \_ 1:0:0:2 sdg 8:96 [active][ready] ^ ^ ^ ^ ^ | | | | |________ Physical Path State | | | |______________ DM Path State | | |____________________ Device Major/Minor Numbers | |_____
# multipath -ll mpath19 (360001ff0721160000000002688e10002) dm-2 DDN,S2A 6620 [size=21T][features=1 queue_if_no_path][hwhandler=0][rw] \_ round-robin 0 [prio=50][active] \_ 1:0:0:2 sdg 8:96 [active][ready] \_ round-robin 0 [prio=10][enabled] \_ 2:0:0:2 sdf 8:80 [active][ready] Path Group 2 \_ round-robin 0 [prio=10][enabled] \_ 2:0:0:2 sdf 8:80 [active][ready] The example above shows a second path group to the same device (referenced in Path Group 1) within the Priority Group.
9. MULTIPATH -LL OUTPUT WITH SLES 11 AND RHEL 6 Under RHEL 6 and SLES 11, the version of multipath tools now displays the same information with very slight changes to the formatting, as show in the example below: RHEL 6.0: 360001ff0802bd0000000004a8f950003 dm-12 DDN,SFA 10000 size=7.
10. KNOWN ISSUES 10.1 RHEL5X/SLES10X 10.1.1 INFINIBAND SCSI DEVICES THAT DISAPPEAR AND COME BACK ARE NOT ADDED TO MULTIPATH DEVICE MAPS (INFINIBAND ONLY) Description: IBSRP changes the host number of the SRP host thereby causing the sysfs path of the device to change. For example LUN 13 = host:bus:target:lun = 6:0:0:13 before the paths fail and then LUN 13 = 7:0:0:13 after the paths come back. Multipath caches the sysfs entries for devices to prevent repeated path lookups.
10.3 VARIOUS 10.3.1 DEFAULT FOR PG_PRIO_CALC HAS CHANGED BETWEEN MULTIPATH VERSION 0.4.8 AND 0.4.9 Description: The default for pg_prio_calc method has changed from “sum” in 0.4.8 to “avg” in 0.4.9. With 0.4.8 (pg_prio_calc = “sum”) the priority of the path group is set to the sum of all path weights in the group. Thus in the priority group below the priority is 600, which is the sum of the six available paths which each have an individual path priority of 100.
