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Re: [dm-devel] mpath_ctl observation + some novice questions


Next topic.  I'm a real dm novice user.  I have not
figured out how to create the disk devices and lvm fs. Is there a doc on how to do this? My guess is that I need to map the wwid in multipath.conf. Is this demonstrated
somewhere?  Thanks.

use a test environment, no production server!


1.) load dm-mapper and HBA kernel modules

2.) create partitions on each lun (e.g.: lun0 has two paths sda and sdb - "fdisk sda" creates the partitions for sda _and_ sdb) - you have to do this step _before_ creating multipath devices (kpartx in /etc/dev.d/block/multipath.dev reads this partition information)

3.) create /etc/multipath.conf

- check multipath.conf.annotated and multipath.conf.synthetic in the multipath-tools tarball
- get lun wwid's with "scsi_id -g -u -s /block/sd?"
- create a "multipath { ... }" section for each lun (define "wwid" and "alias")
- create a "device { ... }" section for your storage (see "TestedEnvironments" located at the multipath-tools homepage) - set "path_grouping_policy" and "prio_callout" (setting "prio_callout" is important. if you choose a wrong value, you will see nothing after starting multipath)

4.) start multipathd (debug with "-d" or "-v4" (syslog))

5.) run "multipath /dev/sd?" for each sd? device

multipath should create device-mapper table entries (see "dmsetup table"), block-device-files in /dev/mapper/ and links in /dev/ for the lun and for each partition

e.g.: you have created two partitions and your lun alias is "yellow" (defined in /etc/multipath.conf):

# dmsetup table
yellow1: ...
yellow: ...
yellow2: ...

# ls /dev/mapper/
yellow yellow1 yellow2 control

# ls -F /dev/yellow*
/dev/yellow@  /dev/yellow1@  /dev/yellow2@

and check "multipath [-v3] -ll"

6.) create filesystems and mount /dev/yellow1 and /dev/yellow2

you can delete the current configuration with "dmsetup remove yellow2; dmsetup remove yellow1; dmsetup remove yellow"

hope that helps

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