[gentoo-user] multipath.conf : learning how to use

["Stefan G. Weichinger" <lists@xunil.at>]

At a customer I have to check through an older gentoo server.

The former admin is not available anymore and among other things I have
to check how the SAN storage is attached.

As I have to plan a new installation with minimal downtime I'd like to
understand that multipath-stuff before any changes ;-)

The system runs:

sys-fs/multipath-tools-0.5.0-r1

and has a multipath.conf:

(rm-ed comments)

defaults {
#  udev_dir                /dev
  polling_interval        15
#  selector                "round-robin 0"
  path_grouping_policy    group_by_prio
  failback                5
  path_checker            tur
#  prio_callout            "/sbin/mpath_prio_tpc /dev/%n"
  rr_min_io               100
  rr_weight               uniform
  no_path_retry           queue
  user_friendly_names     yes

}
blacklist {
  devnode cciss
  devnode fd
  devnode hd
  devnode md
  devnode sr
  devnode scd
  devnode st
  devnode ram
  devnode raw
  devnode loop
  devnode sda
  devnode sdb
}

multipaths {
  multipath {
    wwid  3600c0ff0001e91b2c1bae25601000000
    ## To find your wwid, please use /usr/bin/sg_vpd --page=di /dev/DEVICE.
    ## The address will be a 0x6. Remove the 0x and replace it with 3.
    alias MSA2040_SAMBA_storage
  }
}





"multipath -l" and "-ll" show nothing.

dmesg:

# dmesg | grep multi
[    1.144947] md: multipath personality registered for level -4
[    1.145679] device-mapper: multipath: version 1.9.0 loaded
[    1.145857] device-mapper: multipath round-robin: version 1.0.0 loaded
[21827451.284100] device-mapper: table: 253:0: multipath: unknown path
selector type
[21827451.285432] device-mapper: table: 253:0: multipath: unknown path
selector type
[21827496.130239] device-mapper: table: 253:0: multipath: unknown path
selector type
[21827496.131379] device-mapper: table: 253:0: multipath: unknown path
selector type
[21827497.576482] device-mapper: table: 253:0: multipath: unknown path
selector type

-

I see two devices sdc and sdd that should come from the SAN.

Could someone help me to research this in more detail?

This is a production server, I can't change much ...

I would like to find out how to reliably mount these SAN-devices into a
new OS (maybe a new gentoo installation is coming).

thanks, Stefan