Zakladni prikazy:

• zobrazeni aktivnich multipathu:

  multipath -ll

• reload podle kofigurace:

  multipath -v2

• nastavuje failover nad storage pripojnou pomoci FC a iSCSI
• blacklistuje vsechna zarizeni mimo tech s wwid uvedenym v blacklist exceptions
• multipathy uvadime v sekci multipaths, aby dostali hezke jmeno :)

blacklist {
        wwid .*
}
blacklist_exceptions {
        property "(ID_WWN|SCSI_IDENT_.|ID_SERIAL)"
        wwid "26261353635663533|2317936357870636c"
}
 
defaults {
#                verbosity 6
                failback        manual
                path_grouping_policy  failover
                features "0"
                no_path_retry fail
}
multipaths {
       multipath {
              wwid              26261353635663533
              alias             backup
        }
       multipath {
              wwid              2317936357870636c
              alias             mach3
        }
}

• pridavame zarizeni jehoz jedna z cest je /dev/sdh
• zjistime si jeho scsi_id (wwid) nasledujicim prikazem:

  /lib/udev/scsi_id -u -g -v /dev/sdh
  2317936357870636c

• pridame ho do konfigurace do sekce blacklist_exceptions (oddelovac je |):

  wwid "26261353635663533|2317936357870636c"

• dale do sekce multipaths pridame jeho zaznam:

  multipath {
          wwid              2317936357870636c
          alias             mach3
  }

• nacteme konfiguraci:

  multipath -v2
  create: mach3 (2317936357870636c) undef SCST_FIO,raid-disk
  size=9.1T features='0' hwhandler='0' wp=undef
  |-+- policy='service-time 0' prio=1 status=undef
  | `- 1:0:2:1  sdh  8:112  undef ready running
  `-+- policy='service-time 0' prio=1 status=undef
    `- 15:0:0:1 sdj  8:144  undef ready running

• overime, ze multipath funguje:

  multipath -ll
  backup (26261353635663533) dm-0 SCST_FIO,raid-disk
  size=11T features='0' hwhandler='0' wp=rw
  |-+- policy='service-time 0' prio=1 status=active
  | `- 1:0:1:1  sddf 70:208 active ready running
  `-+- policy='service-time 0' prio=1 status=enabled
    `- 14:0:0:1 sdm  8:192  active ready running
  mach3 (2317936357870636c) dm-80 SCST_FIO,raid-disk
  size=9.1T features='0' hwhandler='0' wp=rw
  |-+- policy='service-time 0' prio=1 status=active
  | `- 1:0:2:1  sdh  8:112  active ready running
  `-+- policy='service-time 0' prio=1 status=enabled
    `- 15:0:0:1 sdj  8:144  active ready running

• vzniklo nam zarizeni /dev/mapper/mach3, ktere pouzivame stejne jako jakekoli jine blokove zarizeni

1) vyradit jednu z cest

echo offline > /sys/block/ [device name] /device/state

2) cestu vratit zpet

echo running > /sys/block/ [device name] /device/state

Je to vhodne udelat po automatickem failover v pripade, ze se prepne cesta z fc na iscsi. Je nastaveno nevracet se zpet, takze zabitim aktivniho ISCSI donutime multipath zase zacit pouzivat FC