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Thursday, November 27, 2008

Linux native multipathing and EMC CX300


a few days ago i got 2 new machines, which should be connected to EMC CX300.

Dell 2950 hardware with QLogic 2432 HBAs.

To retrieve the HBA WWN i did 'cat /sys/class/fc_host/host$1/port_name'

To use failover for more than one HBA use the following entry depending on the hardware vendor:

For QLogic hostbus adapter:
options qla2xxx qlport_down_retry=1 ql2xfailover=0 ql2xretrycounts=5

For Emulex hostbus adapter:
options lpfc lpfc_nodev_tmo=14 lpfc_lun_queue_depth=30 lpfc_discovery_threads=1

in you /etc/modprobe.conf.local

I went to EMC web gui Navisphere and configured a new RAID group.
After that two host groups where created, where the LUN was assigned. This produces and error message in Navisphere telling you about not to add a LUN to different host groups. It can be safely ignored.

I setup the SAN switches zoning and installed Naviagent on the two machines and started the agent. They registered sucessfull and could be found in Navisphere. I assigned each host to it's host group.

I had to setup failover mode on CX300 to 1, otherwise the Linux dmp driver tells the path is faulty.

On the Linux host i created a multipath.conf file and added the local SCSI controller to be blacklisted.
For SuSE 10.1 i used the following:

--------------------/etc/multipath.conf SuSE 10.1 ------------------------------------
## This is the /etc/multipath.conf file recommended for
## EMC storage devices.
## OS : SLES 9 SP3/ SLES 10 SP1
## Arrays : CLARiiON and SYMMETRIX
## The blacklist is the enumeration of all devices that are to be
## excluded from multipath control
devnode_blacklist {
## Replace the wwid with the output of the command
## 'scsi_id -g -u -s /block/[internal scsi disk name]'
## Enumerate the wwid for all internal scsi disks.
## PLEASE CHANGE WWID to fit you needs
wwid 36001ec90e72e4c0010402ffc04201bbc
devnode "^(ram|raw|loop|fd|md|dm-|sr|scd|st)[0-9]*"
devnode "^hd[a-z][[0-9]*]"
devnode "^cciss!c[0-9]d[0-9]*[p[0-9]*]"
devices {
## Device attributes for EMC SYMMETRIX
device {
vendor "EMC "
product "SYMMETRIX"
path_grouping_policy multibus
getuid_callout "/sbin/scsi_id -g -u -s /block/%n"
path_selector "round-robin 0"
features "0"
hardware_handler "0"
failback immediate
## Device attributes for EMC CLARiiON
## Device attributes for EMC CLARiiON
device {
vendor "DGC"
product "*"
path_grouping_policy group_by_prio
getuid_callout "/sbin/scsi_id -g -u -s /block/%n"
prio_callout "/sbin/mpath_prio_emc /dev/%n"
hardware_handler "1 emc"
features "1 queue_if_no_path"
no_path_retry 300
path_checker emc_clariion
failback immediate
------------------------------end /etc/multipath.conf SuSE 10.1---------------------------------
In the blacklist section the 'wwid' entry should be configure to fit your needs, in my case this does exclude internal controllers from being multipathed.

For SuSE 10.2 you may not define the device sections, they are obsolete. Other entries are the same.

After running 'chkconfig boot.multipath on' and 'chkconfig multipathd on' i run 'multipath -d -v2' and found the ouput showing all paths to the devices. 'multipath -v2 ' shows the newly created device /dev/dm-0.

You can view your setup using 'dmsetup -v status ' and 'dmsetup -v ls'.

'dmsetup -v status' shows:

Name: 360060160c11219002cac56035689dd11
Tables present: LIVE
Open count: 4
Event number: 1
Major, minor: 253, 0
Number of targets: 1
UUID: mpath-360060160c11219002cac56035689dd11

0 209715200 multipath 1 0 0 2 1 A 0 2 0 8:32 A 0 8:48 A 0 E 0 2 0 8:16 A 0 8:64
A 0

Also you can view the path status and device with 'multipath -ll'

360060160c11219002cac56035689dd11dm-0 DGC,RAID 5
[size=100G][features=1 queue_if_no_path][hwhandler=1 emc]
\_ round-robin 0 [prio=2][active]
\_ 1:0:1:0 sdc 8:32 [active][ready]
\_ 2:0:0:0 sdd 8:48 [active][ready]
\_ round-robin 0 [prio=0][enabled]
\_ 1:0:0:0 sdb 8:16 [active][ready]
\_ 2:0:1:0 sde 8:64 [active][ready]

This can from this point used like a normal harddisk device which can be partitioned and so on.

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