possible to use 1 drive as hot failover for 2 raid1's?

possible to use 1 drive as hot failover for 2 raid1's?

[Dan Hollis]

We have 5 drives, 2 for raid1-md0 and 2 for raid1-md1. they are all the 
exact same model and partitioned exactly the same. we also have a 5th 
drive we want to use as hot-failover.

is it possible to use the single drive as hot-failover for both md0 and 
md1?

please respond in email as i am not subscribed to the list.

-Dan
-- 
[-] Omae no subete no kichi wa ore no mono da. [-]

Re: possible to use 1 drive as hot failover for 2 raid1's?

[Lars Marowsky-Bree]

On 2003-10-06T16:27:59,
   Dan Hollis <goemon@anime.net> said:

> is it possible to use the single drive as hot-failover for both md0 and 
> md1?

In theory yes, in practice not.

One could imagine (rather easily) a global hot-spare pool for all mds,
but it's not implemented right now.


Sincerely,
    Lars Marowsky-Brée <lmb@suse.de>

-- 
High Availability & Clustering		ever tried. ever failed. no matter.
SuSE Labs				try again. fail again. fail better.
Research & Development, SUSE LINUX AG		-- Samuel Beckett

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Re: possible to use 1 drive as hot failover for 2 raid1's?

[Holger Kiehl]

On Tue, 7 Oct 2003, Lars Marowsky-Bree wrote:

> On 2003-10-06T16:27:59,
>    Dan Hollis <goemon@anime.net> said:
> 
> > is it possible to use the single drive as hot-failover for both md0 and 
> > md1?
> 
> In theory yes, in practice not.
> 
> One could imagine (rather easily) a global hot-spare pool for all mds,
> but it's not implemented right now.
> 
Not sure about this but I thought this would be possible by using mdadm
in monitor mode? In the manpage of mdadm it says:

   As  well  as  reporting  events,  mdadm may move a spare drive from one
   array to another if they are in the same spare-group and if the  desti-
   nation array has a failed drive but not spares.

But I don't know how to create a spare-groupi or what is meant by it?

Regards,
Holger

Re: possible to use 1 drive as hot failover for 2 raid1's?

[Neil Brown]

On Tuesday October 7, Holger.Kiehl@dwd.de wrote:
> On Tue, 7 Oct 2003, Lars Marowsky-Bree wrote:
> 
> > On 2003-10-06T16:27:59,
> >    Dan Hollis <goemon@anime.net> said:
> > 
> > > is it possible to use the single drive as hot-failover for both md0 and 
> > > md1?
> > 
> > In theory yes, in practice not.
> > 
> > One could imagine (rather easily) a global hot-spare pool for all mds,
> > but it's not implemented right now.
> > 
> Not sure about this but I thought this would be possible by using mdadm
> in monitor mode? In the manpage of mdadm it says:
> 
>    As  well  as  reporting  events,  mdadm may move a spare drive from one
>    array to another if they are in the same spare-group and if the  desti-
>    nation array has a failed drive but not spares.
> 
> But I don't know how to create a spare-groupi or what is meant by it?

 From  "man mdadm"

       For  mdadm  to  move  spares  from  one array to another, the different
       arrays need to be labelled with the same spare-group in the  configura-
       tion  file.   The spare-group name can be any string. It is only neces-
       sary that different spare groups use different names.

 from "man mdadm.conf"

           spare-group=
                  The  value  is  a  textual  name for a group of arrays.  All
                  arrays with the same spare-group name are considered  to  be
                  part  of  the  same  group.   The significance of a group of
                  arrays is that mdadm will, when monitoring the arrays,  move
                  a  spare drive from one array in a group to another array in
                  that group if the first array had a failed or missing  drive
                  but no spare.


does that help?

NeilBrown

> 
> Regards,
> Holger
> 
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Re: possible to use 1 drive as hot failover for 2 raid1's?

[Luca Berra]

Dan Hollis wrote:

> We have 5 drives, 2 for raid1-md0 and 2 for raid1-md1. they are all the 
> exact same model and partitioned exactly the same. we also have a 5th 
> drive we want to use as hot-failover.
> 
> is it possible to use the single drive as hot-failover for both md0 and 
> md1?
> 

you can do this with mdadm
http://www.cse.unsw.edu.au/~neilb/source/mdadm/