Concurrent mount of XFS over SAN

Concurrent mount of XFS over SAN

[Heilige Gheist]

Is there a way to prevent and/or detect concurrent mount of same XFS
SAN-based partition from several nodes?
I had to fsck a filesystem losing some data after two nodes happily
mounted a filesystem from same SAN-based partition at the same time and
wrote into it.
Thanks!

--alan

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Re: Concurrent mount of XFS over SAN

[Dave Lloyd]

Heilige Gheist wrote:
 > Is there a way to prevent and/or detect concurrent mount of same XFS
 > SAN-based partition from several nodes?
 > I had to fsck a filesystem losing some data after two nodes happily
 > mounted a filesystem from same SAN-based partition at the same time and
 > wrote into it.
 > Thanks!
 >
 > --alan
 >
 > __________________________________________________
 > Do You Yahoo!?
 > Tired of spam?  Yahoo! Mail has the best spam protection around
 > http://mail.yahoo.com
 >
 >

I think that the generally accepted way is to zone at the switch or the
storage array.

-- 
Dave Lloyd
Test Engineer, Exegy, Inc.
314.450.5342
dlloyd@exegy.com

Re: Concurrent mount of XFS over SAN

[Heilige Gheist]

Dave, 
That's 100% correct assuming you prohibit a shared access between the
nodes. I didn't point out that we're dealing with filesystem failover
setup.
It's obvious that I can always fall back to the inter-node heart-beat
to ensure that only one node is mounting the filesystem.
I'm just wondering if there's any facility or accepted practice to
enforce it.

Thanks,
Alan

--- Dave Lloyd <dlloyd@exegy.com> wrote:

> Heilige Gheist wrote:
>  > Is there a way to prevent and/or detect concurrent mount of same
> XFS
>  > SAN-based partition from several nodes?
>  > I had to fsck a filesystem losing some data after two nodes
> happily
>  > mounted a filesystem from same SAN-based partition at the same
> time and
>  > wrote into it.
>  > Thanks!
>  >
>  > --alan
>  >
>  > __________________________________________________
>  > Do You Yahoo!?
>  > Tired of spam?  Yahoo! Mail has the best spam protection around
>  > http://mail.yahoo.com
>  >
>  >
> 
> I think that the generally accepted way is to zone at the switch or
> the
> storage array.
> 
> -- 
> Dave Lloyd
> Test Engineer, Exegy, Inc.
> 314.450.5342
> dlloyd@exegy.com
> 
> 
> 


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Re: Concurrent mount of XFS over SAN

[Jan-Frode Myklebust]

On 2006-08-07, Heilige Gheist <hgheist@yahoo.com> wrote:
> It's obvious that I can always fall back to the inter-node heart-beat
> to ensure that only one node is mounting the filesystem.
> I'm just wondering if there's any facility or accepted practice to
> enforce it.

STONITH (Shoot The Other Node In The Head) trough smart power switches
or management adapters in the node. 

SCSI reserve/release ... No idea how reliable this is on a SAN, but the
ServeRAID-version works great. http://www.linux-ha.org/ServeRAID

Export the volume group, or scsi device on the first node, before
importing/attaching it on the second .. Probably best to use together
with STONITH, in case the first node fails on unmounting/exporting.

BTW: I think XFS on IRIX had the owning node name in the file system header, 
and only would allow this node to mount the fs. But I can't find this now...
Maybe it's gone, or maybe it was in xlv.. ?


  -jf

Re: Concurrent mount of XFS over SAN

[kris buggenhout]

afaik, the node was stored in xlv, which was an extra option in IRIX, ( 
extra license) but this could later be used in CXFS which allows 
multiple machines to mount the same FS read write from a SAN, made for 
clusters, HA and HPC...

knowledge of the node "owning" the device was in there for protection. 
but can be overridden with an xlv command.

kind regards, Kris

Jan-Frode Myklebust wrote:
> On 2006-08-07, Heilige Gheist <hgheist@yahoo.com> wrote:
>   
>> It's obvious that I can always fall back to the inter-node heart-beat
>> to ensure that only one node is mounting the filesystem.
>> I'm just wondering if there's any facility or accepted practice to
>> enforce it.
>>     
>
> STONITH (Shoot The Other Node In The Head) trough smart power switches
> or management adapters in the node. 
>
> SCSI reserve/release ... No idea how reliable this is on a SAN, but the
> ServeRAID-version works great. http://www.linux-ha.org/ServeRAID
>
> Export the volume group, or scsi device on the first node, before
> importing/attaching it on the second .. Probably best to use together
> with STONITH, in case the first node fails on unmounting/exporting.
>
> BTW: I think XFS on IRIX had the owning node name in the file system header, 
> and only would allow this node to mount the fs. But I can't find this now...
> Maybe it's gone, or maybe it was in xlv.. ?
>
>
>   -jf
>
>
>
>
>   

RE: Concurrent mount of XFS over SAN

[Sebastian Brings]

Maybe off topic meanwhile, but both Irix volume managers xlv and xvm
have the owner stored in the header. Xvm also has an understanding of a
cluster owning the volume, which is required for cxfs.

In a failover environment you absolutely have to make sure the failed
machine really has no more access to the volume, preferably by fencing
the FC switch ports, before you mount it on the standby system.
STONITH implementations also work, but still two machines have to agree
on the ownership when the failed machine comes up again.

Cheers
Sebastian

> -----Original Message-----
> From: xfs-bounce@oss.sgi.com [mailto:xfs-bounce@oss.sgi.com] On Behalf
Of
> kris buggenhout
> Sent: Montag, 7. August 2006 13:02
> To: Jan-Frode Myklebust
> Cc: linux-xfs@oss.sgi.com
> Subject: Re: Concurrent mount of XFS over SAN
> 
> afaik, the node was stored in xlv, which was an extra option in IRIX,
(
> extra license) but this could later be used in CXFS which allows
> multiple machines to mount the same FS read write from a SAN, made for
> clusters, HA and HPC...
> 
> knowledge of the node "owning" the device was in there for protection.
> but can be overridden with an xlv command.
> 
> kind regards, Kris
> 
> Jan-Frode Myklebust wrote:
> > On 2006-08-07, Heilige Gheist <hgheist@yahoo.com> wrote:
> >
> >> It's obvious that I can always fall back to the inter-node
heart-beat
> >> to ensure that only one node is mounting the filesystem.
> >> I'm just wondering if there's any facility or accepted practice to
> >> enforce it.
> >>
> >
> > STONITH (Shoot The Other Node In The Head) trough smart power
switches
> > or management adapters in the node.
> >
> > SCSI reserve/release ... No idea how reliable this is on a SAN, but
the
> > ServeRAID-version works great. http://www.linux-ha.org/ServeRAID
> >
> > Export the volume group, or scsi device on the first node, before
> > importing/attaching it on the second .. Probably best to use
together
> > with STONITH, in case the first node fails on unmounting/exporting.
> >
> > BTW: I think XFS on IRIX had the owning node name in the file system
> header,
> > and only would allow this node to mount the fs. But I can't find
this
> now...
> > Maybe it's gone, or maybe it was in xlv.. ?
> >
> >
> >   -jf
> >
> >
> >
> >
> >
>