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Re: [dm-devel] Status of resizing/growing dm-multipath devices on the fly



On Wed, Aug 06, 2008 at 02:58:16PM -0600, Andrew Patterson wrote:
> On Wed, 2008-08-06 at 12:36 -0700, Mike Anderson wrote:
> > Pasi K?rkk?inen <pasik iki fi> wrote:
> > > On Wed, Aug 06, 2008 at 03:48:12PM +0200, Domenico Viggiani wrote:
> > > > * Pasi Kärkkäinen wrote:
> > > > > 
> > > > > Is it possible to resize (grow) dm-multipath devices on the 
> > > > > fly nowadays?
> > > > > 
> > > > > I googled and found some discussions about the subject, but 
> > > > > the conclusion seemed to be it's not possible.. that was a 
> > > > > while ago, so I was wondering if this has been fixed/implemented..
> > > > > 
> > > > > Using LVM and adding another new LUN/PV is not an option 
> > > > > always.. it's a lot easier to manage the whole thing if it's 
> > > > > possible to resize/grow existing LUNs on the fly.
> > > > 
> > > > Nowadays all disk-arrays make online LUN extension a breeze but
> > > > unfortunately it seems that dm-multipath is still not able to see new size
> > > > without downtime:
> > > >  http://www.redhat.com/archives/dm-devel/2007-August/msg00205.html
> > > > Look also at this recent thread on RHEL5 mailing-list where you can find
> > > > also a post from a Red Hat representative:
> > > >  http://www.redhat.com/archives/rhelv5-list/2008-July/msg00267.html
> > > > 
> > > > Sure, you can just add a new LUN, pvcreate and vgextend but it is not a
> > > > viable solution because it causes LUN proliferation.
> > > > 
> > > > Sincerely, I'm still subscribed to this mailing-list only to see if someone
> > > > solve this SHAME!
> > > > It's a feature that Linux really needs.
> > > > 
> > > > Hope someone pick this cry of pain!
> > > > 
> > > 
> > > Thanks for the reply.
> > > 
> > > Does someone know what's the actual problem in this? meaning why it hasn't
> > > been done yet.. 
> > 
> > It has to do with the block layer not using the new size value while there
> > are openers.
> > 
> > Andrew submitted a patch series (url below) a while ago to try and address
> > this issue, but I do not know the status. I added Andrew to the cc.
> > 
> > http://thread.gmane.org/gmane.linux.scsi/41623
> > 
> 
> The above patchset works with SCSI devices. I have tested it with single
> SCSI devices under dm/LVM, i.e., a PV is on a single SCSI LUN with only
> one path to it. It has not yet been accepted upstream due to not getting
> sign-off from Al Viro. I plan on resubmitting soon to add cciss support.
> Hopefully Al will getting around to reviewing it sometime this century.
> I have heard rumors that Al has some all-encompassing solution for this
> problem but hasn't got around to implementing it.  I'll test my new
> patches with multi-path while I am at it.
> 

Was there some problems/issues with the patchset? Or just lack of time from
Al.. 

-- Pasi


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