Multipath Usage Guide available at LVM wiki page

Multipath Usage Guide available at LVM wiki page

[Chandra Seetharaman]

Hi All,

I put the Multipath Usage guide in the LVM wiki page. Here is the link:
http://sources.redhat.com/lvm2/wiki/MultipathUsageGuide

One can reach the same from the lvm wiki homepage
(http://sources.redhat.com/lvm2/wiki/HomePage) through the links "Usage
Documentation" -> "Multipath Usage Guide"

Let me know if you have any comments/suggestions.

regards,

chandra 
-- 

----------------------------------------------------------------------
    Chandra Seetharaman               | Be careful what you choose....
              - sekharan@us.ibm.com   |      .......you may get it.
----------------------------------------------------------------------

Re: Multipath Usage Guide available at LVM wiki page

[Pradipmaya Maharana]

Hi Chandra,

Thanks for the document, it surely is helpful.

I had a query (which I have asked in previous mails), the document
does not talk about how to install SLES on multipath devices with LVM.
Basically I tried installing with creating partitions (for both RHEL
and SLES) and it worked fine; LVM worked fine for RHEL but for SLES it
won't work.

- It won't let me mount-by device-id for LVM
- specifying the volume label won't help.

What am I missing.

Thanks and Regards,
Pradipmaya.


On Jan 24, 2008 10:25 AM, Chandra Seetharaman <sekharan@us.ibm.com> wrote:
> Hi All,
>
> I put the Multipath Usage guide in the LVM wiki page. Here is the link:
> http://sources.redhat.com/lvm2/wiki/MultipathUsageGuide
>
> One can reach the same from the lvm wiki homepage
> (http://sources.redhat.com/lvm2/wiki/HomePage) through the links "Usage
> Documentation" -> "Multipath Usage Guide"
>
> Let me know if you have any comments/suggestions.
>
> regards,
>
> chandra
> --
>
> ----------------------------------------------------------------------
>    Chandra Seetharaman               | Be careful what you choose....
>              - sekharan@us.ibm.com   |      .......you may get it.
> ----------------------------------------------------------------------
>
>
> --
> dm-devel mailing list
> dm-devel@redhat.com
> https://www.redhat.com/mailman/listinfo/dm-devel
>

Re: Multipath Usage Guide available at LVM wiki page

[Chandra Seetharaman]

On Thu, 2008-01-24 at 10:33 -0800, Pradipmaya Maharana wrote:
> Hi Chandra,
> 
> Thanks for the document, it surely is helpful.
> 
> I had a query (which I have asked in previous mails), the document
> does not talk about how to install SLES on multipath devices with LVM.
> Basically I tried installing with creating partitions (for both RHEL
> and SLES) and it worked fine; LVM worked fine for RHEL but for SLES it
> won't work.
> 
> - It won't let me mount-by device-id for LVM
> - specifying the volume label won't help.

You could put your lvm on top of the multipathed dm-device. For which
you may have to disable lvm probing in the initrd phase. You can do this
by changing your /etc/lvm/lvm.conf and then running mkinitrd.

You have to change the filter line to be like this:

filter = [ "a|/dev/mapper.*|", "a|/dev/disk/by-name/.*|", "r|.*|" ]

Let me know if this helps.
> 
> What am I missing.
> 
> Thanks and Regards,
> Pradipmaya.
> 
> 
> On Jan 24, 2008 10:25 AM, Chandra Seetharaman <sekharan@us.ibm.com> wrote:
> > Hi All,
> >
> > I put the Multipath Usage guide in the LVM wiki page. Here is the link:
> > http://sources.redhat.com/lvm2/wiki/MultipathUsageGuide
> >
> > One can reach the same from the lvm wiki homepage
> > (http://sources.redhat.com/lvm2/wiki/HomePage) through the links "Usage
> > Documentation" -> "Multipath Usage Guide"
> >
> > Let me know if you have any comments/suggestions.
> >
> > regards,
> >
> > chandra
> > --
> >
> > ----------------------------------------------------------------------
> >    Chandra Seetharaman               | Be careful what you choose....
> >              - sekharan@us.ibm.com   |      .......you may get it.
> > ----------------------------------------------------------------------
> >
> >
> > --
> > dm-devel mailing list
> > dm-devel@redhat.com
> > https://www.redhat.com/mailman/listinfo/dm-devel
> >
-- 

----------------------------------------------------------------------
    Chandra Seetharaman               | Be careful what you choose....
              - sekharan@us.ibm.com   |      .......you may get it.
----------------------------------------------------------------------

Re: Multipath Usage Guide available at LVM wiki page

[malahal]

Chandra Seetharaman [sekharan@us.ibm.com] wrote:
> On Thu, 2008-01-24 at 10:33 -0800, Pradipmaya Maharana wrote:
> > Hi Chandra,
> > 
> > Thanks for the document, it surely is helpful.
> > 
> > I had a query (which I have asked in previous mails), the document
> > does not talk about how to install SLES on multipath devices with LVM.
> > Basically I tried installing with creating partitions (for both RHEL
> > and SLES) and it worked fine; LVM worked fine for RHEL but for SLES it
> > won't work.
> > 
> > - It won't let me mount-by device-id for LVM
> > - specifying the volume label won't help.

Are you saying it won't help or it did NOT help?
 
> You could put your lvm on top of the multipathed dm-device. For which
> you may have to disable lvm probing in the initrd phase. You can do this
> by changing your /etc/lvm/lvm.conf and then running mkinitrd.
> 
> You have to change the filter line to be like this:
> 
> filter = [ "a|/dev/mapper.*|", "a|/dev/disk/by-name/.*|", "r|.*|" ]
> 
> Let me know if this helps.

multipath should be run before lvm (even in initrd), if so, how does
this filter help?  LVM will not be able to claim plain devices in the
presence of multipath devices anyway, right?

Re: Multipath Usage Guide available at LVM wiki page

[Chandra Seetharaman]

On Thu, 2008-01-24 at 18:14 -0800, malahal@us.ibm.com wrote:
> Chandra Seetharaman [sekharan@us.ibm.com] wrote:
> > On Thu, 2008-01-24 at 10:33 -0800, Pradipmaya Maharana wrote:
> > > Hi Chandra,
> > > 
> > > Thanks for the document, it surely is helpful.
> > > 
> > > I had a query (which I have asked in previous mails), the document
> > > does not talk about how to install SLES on multipath devices with LVM.
> > > Basically I tried installing with creating partitions (for both RHEL
> > > and SLES) and it worked fine; LVM worked fine for RHEL but for SLES it
> > > won't work.
> > > 
> > > - It won't let me mount-by device-id for LVM
> > > - specifying the volume label won't help.
> 
> Are you saying it won't help or it did NOT help?
> 
> > You could put your lvm on top of the multipathed dm-device. For which
> > you may have to disable lvm probing in the initrd phase. You can do this
> > by changing your /etc/lvm/lvm.conf and then running mkinitrd.
> > 
> > You have to change the filter line to be like this:
> > 
> > filter = [ "a|/dev/mapper.*|", "a|/dev/disk/by-name/.*|", "r|.*|" ]
> > 
> > Let me know if this helps.
> 
> multipath should be run before lvm (even in initrd), if so, how does
> this filter help?  LVM will not be able to claim plain devices in the
> presence of multipath devices anyway, right?

It can. I have seen it happen (in sles9 though). multipath opens the
(sd) device and later lvm scans the same device, it fails (as there is
already an open reference). 

The filter above helps in making lvm read the multipathed device instead
of the underlying scsi device, and hence the lvm scan succeeds.

> 
> --
> dm-devel mailing list
> dm-devel@redhat.com
> https://www.redhat.com/mailman/listinfo/dm-devel
-- 

----------------------------------------------------------------------
    Chandra Seetharaman               | Be careful what you choose....
              - sekharan@us.ibm.com   |      .......you may get it.
----------------------------------------------------------------------

Re: Multipath Usage Guide available at LVM wiki page

[root]

Chandra Seetharaman [sekharan@us.ibm.com] wrote:
> 
> It can. I have seen it happen (in sles9 though). multipath opens the
> (sd) device and later lvm scans the same device, it fails (as there is
> already an open reference). 

That is expected but LVM should continue to scan rest of the devices
including our multipath devices. If LVM fails to scan rest of the
devices, then it should be a bug!