partitioning multipath device

partitioning multipath device

[Ron Peterson]

The multipath-tools FAQ has the following to say about partitioning
multipath devices.

From http://christophe.varoqui.free.fr/faq.html

> 6. How do I partition my multipathed devices
> Partition a constituant path instead. And reload the map through multipath(8)

I take this to mean, for example, that one should partition /dev/sdX,
rather than the corresponding coalesced /dev/mapper/... device, correct?

My question is: why?  Paritioning the /dev/mapper device appears to
work.  Is there an operational difference?  I've always done this
exactly as advised, but I know someone who didn't, and we're wondering
if it matters.

TIA

-Ron-

Re: partitioning multipath device

[Christophe Varoqui]

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The device mapper used to eat ioctl. This is no longer the case. I'll fix the faq.
Thanks for the heads-up.

----- Message d'origine -----
> The multipath-tools FAQ has the following to say about partitioning
> multipath devices.
>
> > From http://christophe.varoqui.free.fr/faq.html
>
> > 6. How do I partition my multipathed devices
> > Partition a constituant path instead. And reload the map through multipath(8)
>
> I take this to mean, for example, that one should partition /dev/sdX,
> rather than the corresponding coalesced /dev/mapper/... device, correct?
>
> My question is: why?  Paritioning the /dev/mapper device appears to
> work.  Is there an operational difference?  I've always done this
> exactly as advised, but I know someone who didn't, and we're wondering
> if it matters.
>
> TIA
>
> -Ron-
>
> --
> dm-devel mailing list
> dm-devel@redhat.com
> https://www.redhat.com/mailman/listinfo/dm-devel


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Re: partitioning multipath device

[Bryn M. Reeves]

On Fri, 2010-01-22 at 14:29 -0500, Ron Peterson wrote:
> The multipath-tools FAQ has the following to say about partitioning
> multipath devices.
> 
> >From http://christophe.varoqui.free.fr/faq.html
> 
> > 6. How do I partition my multipathed devices
> > Partition a constituant path instead. And reload the map through multipath(8)
> 
> I take this to mean, for example, that one should partition /dev/sdX,
> rather than the corresponding coalesced /dev/mapper/... device, correct?
> 
> My question is: why?  Paritioning the /dev/mapper device appears to
> work.  Is there an operational difference?  I've always done this
> exactly as advised, but I know someone who didn't, and we're wondering
> if it matters.

It doesn't actually matter too much. If you're partitioning before
assembling maps then you may as well do it on a path. The common
partitioning tools should do the right thing if you point them at the
multipath device too though (although you may need to arrange for kpartx
to get run again, or run it manually to refresh).

Regards,
Bryn.