[linux-lvm] multipath question

[linux-lvm] multipath question

[vu pham]

I set up multipath on /dev/sda and /dev/sdb which are mapped from a 
remote single disk, which has two partitions.

Below are some output.
[root@vm5 mpath]# ls -l
total 0
lrwxrwxrwx 1 root root 7 Mar 19 10:34 mpath0 -> ../dm-2
lrwxrwxrwx 1 root root 7 Mar 19 10:34 mpath0p1 -> ../dm-3
lrwxrwxrwx 1 root root 7 Mar 19 10:34 mpath0p2 -> ../dm-4

[root@vm5 mpath]# multipath -ll
mpath0 (16465616462656166313a3100000000000000000000000000) dm-2 
IET,VIRTUAL-DISK
[size=5.0G][features=0][hwhandler=0]
\_ round-robin 0 [prio=0][active]
  \_ 0:0:0:1 sda 8:0   [active][ready]
\_ round-robin 0 [prio=0][enabled]
  \_ 1:0:0:1 sdb 8:16  [active][ready]
[root@vm5 mpath]#


 From the multipath command, I know dm-2 is mapped from two devices 
/dev/sda and /dev/sdb as expected.

But how can I know if dm-3 is mapped from /dev/sda1 and /dev/sdb1, and 
dm-4 from /dev/sda2 and /dev/sdb2 ?

The command "multipath -ll" only gives info on mpath0 or dm-2.

I tried  multipath -ll /dev/mpath/mpath0p1 but does not show anything.

Thanks,

Vu

Re: [linux-lvm] multipath question

[Chandra Seetharaman]

On Thu, 2009-03-19 at 13:00 -0600, vu pham wrote:
> I set up multipath on /dev/sda and /dev/sdb which are mapped from a 
> remote single disk, which has two partitions.
> 
> Below are some output.
> [root@vm5 mpath]# ls -l
> total 0
> lrwxrwxrwx 1 root root 7 Mar 19 10:34 mpath0 -> ../dm-2
> lrwxrwxrwx 1 root root 7 Mar 19 10:34 mpath0p1 -> ../dm-3
> lrwxrwxrwx 1 root root 7 Mar 19 10:34 mpath0p2 -> ../dm-4
>
> [root@vm5 mpath]# multipath -ll
> mpath0 (16465616462656166313a3100000000000000000000000000) dm-2 
> IET,VIRTUAL-DISK
> [size=5.0G][features=0][hwhandler=0]
> \_ round-robin 0 [prio=0][active]
>   \_ 0:0:0:1 sda 8:0   [active][ready]
> \_ round-robin 0 [prio=0][enabled]
>   \_ 1:0:0:1 sdb 8:16  [active][ready]
> [root@vm5 mpath]#
> 
> 
>  From the multipath command, I know dm-2 is mapped from two devices 
> /dev/sda and /dev/sdb as expected.
> 
> But how can I know if dm-3 is mapped from /dev/sda1 and /dev/sdb1, and 
> dm-4 from /dev/sda2 and /dev/sdb2 ?
> 
> The command "multipath -ll" only gives info on mpath0 or dm-2.
> 
> I tried  multipath -ll /dev/mpath/mpath0p1 but does not show anything.

mpath0 is analogous to sda and mpath0p1, mpath0p2 are analogous to sda1,
sda2.

since there is "mpath0" in mpath0p1 and mpath0p2, you can be sure that
they are built off sda and sdb (in effect mpath0p1 is made of sda1 and
sdb1 and so on)...

> 
> Thanks,
> 
> Vu
> 
> _______________________________________________
> linux-lvm mailing list
> linux-lvm@redhat.com
> https://www.redhat.com/mailman/listinfo/linux-lvm
> read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/

Re: [linux-lvm] multipath question

[Vu Pham]

Chandra Seetharaman wrote:
> On Thu, 2009-03-19 at 13:00 -0600, vu pham wrote:
>> I set up multipath on /dev/sda and /dev/sdb which are mapped from a 
>> remote single disk, which has two partitions.
>>
>> Below are some output.
>> [root@vm5 mpath]# ls -l
>> total 0
>> lrwxrwxrwx 1 root root 7 Mar 19 10:34 mpath0 -> ../dm-2
>> lrwxrwxrwx 1 root root 7 Mar 19 10:34 mpath0p1 -> ../dm-3
>> lrwxrwxrwx 1 root root 7 Mar 19 10:34 mpath0p2 -> ../dm-4
>>
>> [root@vm5 mpath]# multipath -ll
>> mpath0 (16465616462656166313a3100000000000000000000000000) dm-2 
>> IET,VIRTUAL-DISK
>> [size=5.0G][features=0][hwhandler=0]
>> \_ round-robin 0 [prio=0][active]
>>   \_ 0:0:0:1 sda 8:0   [active][ready]
>> \_ round-robin 0 [prio=0][enabled]
>>   \_ 1:0:0:1 sdb 8:16  [active][ready]
>> [root@vm5 mpath]#
>>
>>
>>  From the multipath command, I know dm-2 is mapped from two devices 
>> /dev/sda and /dev/sdb as expected.
>>
>> But how can I know if dm-3 is mapped from /dev/sda1 and /dev/sdb1, and 
>> dm-4 from /dev/sda2 and /dev/sdb2 ?
>>
>> The command "multipath -ll" only gives info on mpath0 or dm-2.
>>
>> I tried  multipath -ll /dev/mpath/mpath0p1 but does not show anything.
> 
> mpath0 is analogous to sda and mpath0p1, mpath0p2 are analogous to sda1,
> sda2.
> 
> since there is "mpath0" in mpath0p1 and mpath0p2, you can be sure that
> they are built off sda and sdb (in effect mpath0p1 is made of sda1 and
> sdb1 and so on)...
> 

Chandra, that makes sense. Thanks a lot for your explanation.

Vu