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
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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.
Thanks,
Stephen Kirkpatrick
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