[Linux-cluster] Duplicate Volumes, GFS fail over

[Greg Swift]

Greg Swift wrote:
> isplist at logicore.net wrote:
>> Thanks.
>>
>> I'll look into this.
>> Does this have to be installed on every server in the cluster? 
>> Contacting the vendor won't do me any good since I don't have support 
>> for 90% of the hardware being used :). Has to be something I can do 
>> on my own with what I've got.
>>
>> Mike
>>   
> every box that has multiple paths would need to have it to behave 
> properly.  Like i said before, it might not be that difficult.
> You can use the default /etc/multipath.conf by just commenting out the 
> blacklist section.  My default /etc/multipath.conf looks like this:
>
> devnode_blacklist
> {
>       ##this block the primary local hard disk, change to meet your setup
>       devnode "^sda"
>       ##this ignores lots of stuph that is not relevant at all in most 
> circumstances
>        devnode "^(ram|raw|loop|fd|md|dm-|sr|scd|st)[0-9]*"
>       ##this blocks ide based devices
>        devnode "^hd[a-z][0-9]*"
>       ##i dont remember what this blocks.
>        devnode "^cciss!c[0-9]d[0-9]*[p[0-9]*]"
> }
> defaults {
>        ## use user friendly names, instead of using WWIDs as names.
>        user_friendly_names yes
> }
>
> I define a devices section for the emc box i work with that looks like 
> this:
> devices {
>        ## Device attributes requirements for EMC Symmetrix
>        ## are part of the default definitions and do not require separate
>        ## definition.
>        ## 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"
>                path_checker emc_clariion
>                path_selector "round-robin 0"
>                features "1 queue_if_no_path"
>                no_path_retry 300
>                hardware_handler "1 emc"
>                failback immediate
>        }
> }
>
> but thats not necessary.  it should look at what you have and use 
> defaults based on pre-configured assumptions (correct me if i'm wrong 
> ppl).
>
> -greg
>
wait a minute... this is the procedure i use to turn on multipath (sorry 
i had forgotten that i did more than just turn on the service).

update /etc/multipath.conf
mkinitrd -f /boot/initrd-`uname -r` `uname -r`

reboot

modprobe dm-multipath
modprobe dm-round-robin
service multipathd start

at that point you should be able to do 'multipath -ll' and see your 
multipath setup.

Here is an example from one of my boxes that has 3 luns through 4 paths 
a piece:

[root at phantasos ~]# multipath -ll
mpath2 (36006016003e115003ef0eb769632db11)
[size=191 GB][features="1 queue_if_no_path"][hwhandler="1 emc"]
\_ round-robin 0 [prio=2][active]
 \_ 1:0:3:1 sdg 8:96  [active][ready]
 \_ 2:0:3:1 sdm 8:192 [active][ready]
\_ round-robin 0 [enabled]
 \_ 1:0:2:1 sde 8:64  [active][ready]
 \_ 2:0:2:1 sdk 8:160 [active][ready]

mpath1 (36006016003e11500eefae69dd756da11)
[size=532 GB][features="1 queue_if_no_path"][hwhandler="1 emc"]
\_ round-robin 0 [prio=2][active]
 \_ 1:0:3:0 sdf 8:80  [active][ready]
 \_ 2:0:3:0 sdl 8:176 [active][ready]
\_ round-robin 0 [enabled]
 \_ 1:0:2:0 sdd 8:48  [active][ready]
 \_ 2:0:2:0 sdj 8:144 [active][ready]

mpath0 (360060160a9a01000a23b3bb43cfbda11)
[size=532 GB][features="1 queue_if_no_path"][hwhandler="1 emc"]
\_ round-robin 0 [prio=2][active]
 \_ 1:0:1:0 sdc 8:32  [active][ready]
 \_ 2:0:1:0 sdi 8:128 [active][ready]
\_ round-robin 0 [enabled]
 \_ 1:0:0:0 sdb 8:16  [active][ready]
 \_ 2:0:0:0 sdh 8:112 [active][ready]


the mpathX is the use_friendly_names part of multipathd.conf, else the 
3600* would be the name.

-greg

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