[linux-lvm] LVM Mirroring

[linux-lvm] LVM Mirroring

[Senthil Kumar]

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Hi All,

Is it Possible to create LVM mirroring with out using RAID
If possible can u send related document or URL.
Thanks in  Advance.

Senthilkumar.C


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Re: [linux-lvm] LVM Mirroring

[Marian Csontos]

LVM Mirroring is SW implementation of RAID1, thus no, it is not possible.

Senthil Kumar wrote:
> Hi All,
>
> Is it Possible to create LVM mirroring with out using RAID
> If possible can u send related document or URL.
> Thanks in  Advance.
>
> Senthilkumar.C
>
>
>       Add more friends to your messenger and enjoy! Go to http://messenger.yahoo.com/invite/
>   
> ------------------------------------------------------------------------
>
> _______________________________________________
> 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] LVM Mirroring

[Bryn M. Reeves]

On Wed, 2009-04-22 at 10:34 +0200, Marian Csontos wrote:
> LVM Mirroring is SW implementation of RAID1, thus no, it is not possible.

I think the poster is asking if it's possible to have mirrored LVM
volumes without using an external software or hardware RAID solution
like MD or a hardware RAID controller.

As you point out, LVM2 includes RAID1 (mirroring) so the poster should
be able to do what they want.

Regards,
Bryn.

[linux-lvm] LVM mirroring..

[Prateek Donni]

I have been trying to make use of LVM mirroring to create a data
protection application , i tried configuring it on two disks but it
does not work w/o using --corelog. And secondly i cannot see the
volume which is the mirror using lvscan , but can only be seen in the
GUI.

Kindly help me with this..

Thanks,
 Prateek

Re: [linux-lvm] LVM mirroring..

[Curtis Doty]

Yesterday Prateek Donni said:

> I have been trying to make use of LVM mirroring to create a data
> protection application , i tried configuring it on two disks but it
> does not work w/o using --corelog.

I think you need this or a third disk for log PE if you want mirror to 
persist reboots.

> And secondly i cannot see the volume which is the mirror using lvscan , 
> but can only be seen in the GUI.

Works here with -a and displays both lv target and mimages.

../C

[linux-lvm] lvm mirroring

[Roman Gavrilov]

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Hello,

I have 2 physical discs.
I have 4 partitions on the first disk. 
I created a volume group "lvmhd" from all of the partitions and later created logical volumes.

this is the result from the vgdisplay
--- Volume group ---
VG Name               lvmhd
VG Access             read/write
VG Status             available/resizable
VG #                  0
MAX LV                256
Cur LV                3
Open LV               3
MAX LV Size           2 TB
Max PV                256
Cur PV                4
Act PV                4
VG Size               35.59 GB
PE Size               32 MB
Total PE              1139
Alloc PE / Size       1131 / 35.34 GB
Free  PE / Size       8 / 256 MB
VG UUID               xqamqE-9gSs-Xy3O-2tVQ-wYzy-Cp3u-0Wivbd

and those are the logical volumes
/dev/lvmhd/lvm_usr    3.0G  980M  1.8G  35% /usr
/dev/lvmhd/lvm_var    4.9G   65M  4.6G   2% /var
/dev/lvmhd/lvm_home    27G   33M   25G   1% /home

later I mirrored the first disk to the second disk with dd if=/dev/hda of=/dev/hdb so if the first disk breaks I can remove it and replace it with the second disk and get the server up in minutes.

Now I want to be able to use the second disk while I am running from the first. But the volume groups are the same and I am afraid that if I will recreate the logical volumes I'll ruin some thing on the second disk.
Is there anything I can do about it so I could use the second disk for backups but still have the same architecture as the primary disk ?
is there any way to mount those logical volumes which are mirrors of the primary disk ?
for example I can do 
pvdisplay /dev/hdb3 (this is the slave disk which is the mirror of the primary and its not mounted)
--- Physical volume ---
PV Name               /dev/hdb3
VG Name               lvmhd
PV Size               13.67 GB [28676025 secs] / NOT usable 32.19 MB [LVM: 129 KB]
PV#                   1
PV Status             available
Allocatable           yes (but full)
Cur LV                3
PE Size (KByte)       32768
Total PE              436
Free PE               0
Allocated PE          436
PV UUID               5XenPH-2NLb-cmN0-qEBb-QGuJ-zWxv-otMr7i

thanks

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Re: [linux-lvm] lvm mirroring

[Heinz J . Mauelshagen]

On Sun, Feb 23, 2003 at 03:40:06AM +0200, Roman Gavrilov wrote:
> Hello,
> 
> I have 2 physical discs.
> I have 4 partitions on the first disk. 
> I created a volume group "lvmhd" from all of the partitions and later created logical volumes.
> 
> this is the result from the vgdisplay
> --- Volume group ---
> VG Name               lvmhd
> VG Access             read/write
> VG Status             available/resizable
> VG #                  0
> MAX LV                256
> Cur LV                3
> Open LV               3
> MAX LV Size           2 TB
> Max PV                256
> Cur PV                4
> Act PV                4
> VG Size               35.59 GB
> PE Size               32 MB
> Total PE              1139
> Alloc PE / Size       1131 / 35.34 GB
> Free  PE / Size       8 / 256 MB
> VG UUID               xqamqE-9gSs-Xy3O-2tVQ-wYzy-Cp3u-0Wivbd
> 
> and those are the logical volumes
> /dev/lvmhd/lvm_usr    3.0G  980M  1.8G  35% /usr
> /dev/lvmhd/lvm_var    4.9G   65M  4.6G   2% /var
> /dev/lvmhd/lvm_home    27G   33M   25G   1% /home
> 
> later I mirrored the first disk to the second disk with dd if=/dev/hda of=/dev/hdb so if the first disk breaks I can remove it and replace it with the second disk and get the server up in minutes.

This is a copy, no mirror.

> 
> Now I want to be able to use the second disk while I am running from the first. But the volume groups are the same and I am afraid that if I will recreate the logical volumes I'll ruin some thing on the second disk.
> Is there anything I can do about it so I could use the second disk for backups but still have the same architecture as the primary disk ?

With LVM1 rename /dev/hdb to /dev/myhdb, with LVM2 you could change
the device name filter in a configfile.

> is there any way to mount those logical volumes which are mirrors of the primary disk ?
> for example I can do 
> pvdisplay /dev/hdb3 (this is the slave disk which is the mirror of the primary and its not mounted)
> --- Physical volume ---
> PV Name               /dev/hdb3
> VG Name               lvmhd
> PV Size               13.67 GB [28676025 secs] / NOT usable 32.19 MB [LVM: 129 KB]
> PV#                   1
> PV Status             available
> Allocatable           yes (but full)
> Cur LV                3
> PE Size (KByte)       32768
> Total PE              436
> Free PE               0
> Allocated PE          436
> PV UUID               5XenPH-2NLb-cmN0-qEBb-QGuJ-zWxv-otMr7i
> 
> thanks

You would need to change the LVM metadata to do this.

The correct way to have a copy of your VG would have been
to create a second VG which must have a different name from the first one
with PV hdb in it, create all the LVs you have in "lvmhd", which can have the
same names as in "lvmhd" and dd the LVs over.

I presume your VG "lvmhd" takes no writes during the copy.

-- 

Regards,
Heinz    -- The LVM Guy --

*** Software bugs are stupid.
    Nevertheless it needs not so stupid people to solve them ***

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Heinz Mauelshagen                                 Sistina Software Inc.
Senior Consultant/Developer                       Am Sonnenhang 11
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                                                  Germany
Mauelshagen@Sistina.com                           +49 2626 141200
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[linux-lvm] lvm mirroring

[Sebastian Tomac]

Correct me if I'm wrong, but if I read the LVM-0.8 code right there is
no mirroring  implemented.  Both AIX and Solaris lvm has mirroring
capabilities (sk. lv copies).

If there is interest to enable this feature in LVM, I  would be prepared
to start working on it.

Let me know...

regards
Sebastian

Re: [linux-lvm] lvm mirroring

[Heinz J. Mauelshagen]

On Fri, Jan 21, 2000 at 03:32:43PM +0100, Sebastian Tomac wrote:
> Correct me if I'm wrong, but if I read the LVM-0.8 code right there is
> no mirroring  implemented.  Both AIX and Solaris lvm has mirroring
> capabilities (sk. lv copies).

Yes, i know :-)

> 
> If there is interest to enable this feature in LVM, I  would be prepared
> to start working on it.
> 
> Let me know...

Great offer.
Thanks a lot!

What about metadata (VGDA) mirroring as well?
IMO this is necessary too, because data mirroring is not usefull if
we get rid of our metadata which will lead to unaccessable data anyway.

Could you provied your concept ideas?

Regards,
Heinz