[Linux-cluster] High Availability options

Stephen Kirkpatrick stephenk at olcinc.com
Thu Jul 13 19:45:49 UTC 2006

Lon Hohberger wrote:
> On Thu, 2006-07-13 at 12:14 -0500, Stephen Kirkpatrick wrote:
>> Thanks for the reply.  I wondered if it was possible to have HA for 
>> stateful applications.  At least
>> I know my options better now.  I can tolerate brief downtime, like the 
>> time it would take a failover
>> node to take over, although no downtime would have been preferred.
>> Any suggestions on HA solutions for a non-SAN deployment?
> You don't need a SAN if you don't intend to share data.  
> If you intend to share data but do not want a SAN, you'll need to set up
> DRBD or CLVM+Cluster Mirroring+GNBD (Note: cluster mirroring is still in
> a bit of development).  The main advantage to the latter approach is
> simultaneous read/write access from both machines in the cluster.  The
> advantage to DRBD is that it is easier to set up.
> Alternatively, you could use NFS mounts from a good NAS (a NetApp filer,
> as an example) as your source for shared dat.
> You can use linux-cluster or Linux-HA to do failover with or without a
> SAN; the choice is up to you.  Linux-HA supports DRBD out of the box,
> but CLVM will still need parts of linux-cluster running in order to
> operate.
> If you want support, you can use Red Hat Cluster Suite (which is
> effectively linux-cluster w/ support).
> Good luck!
> -- Lon
> --
> Linux-cluster mailing list
> Linux-cluster at redhat.com
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Thanks for the info.  If I understood correctly what I was reading
about DRDB, it sounds like it runs entirely over an IP network.
This sounds like what I had originally envisioned for this project,
as it is a small deployment.

I was envisioning SCSI storage in two nodes with individual
internal RAID arrays as depicted in the diagram below,

+----------------+          +------------------+
| Primary server |            | Secondary server |
|                |            |                  |
|  -----------   |/          \|   -----------    |
|     RAID-1     |------------|      RAID-1      |
|  -----------   |\    |     /|   -----------    |
|                |     |      |                  |
+----------------+     |      +------------------+
                       +-- Data sync over IP network?

I was thinking fibre channel storage when I said no SAN.  The
cost of deploying fibre storage is a bit much for this small
project.  However, if there is a good way to utilize shared
SCSI storage and a good HA solution to go along, I would be open
to researching it.

In your response, you indicated that Linux-HA supports DRDB out
of the box.  Does the Red Hat Cluster Suite support this too?
The Cluster Project FAQ just mentions the CLVM/GNBD solution.

Stephen Kirkpatrick

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