topic Re: MSA500, 4 Servers, redundant controller in Disk Enclosures

MSA500, 4 Servers, redundant controller

Gerald Hochegger — Thu, 17 Nov 2005 04:52:00 GMT

Hello,

I searched the HP site, asked our reseller,..
but could not find definitive answers for
my planned configuration.

I want to attach four DL-380, DL-385
Servers running Linux to a MSA500 G2 with
a 4-port IO/Card and a redundant controller.
(4-node shared storage configuration)

I do not need multipath, and other cluster
features - the Linux Servers should use
the standard cciss driver only - but I need
the redundant controller failover.

So - what happens in a 4-node shared storage
configuration with a redundant controller
if the active controller fails:

* the redundant controller takes over
seemlessly ? (that would be nice)
* All 4 servers loose the connection to the
MSA500
(until somebody activates the redundant
controller)

Can somebody please tell me what would really
happen with this configuration.

Thanks,
Gerald

Re: MSA500, 4 Servers, redundant controller

Basil Vizgin_1 — Thu, 17 Nov 2005 05:07:47 GMT

The redundant controller takes over seamlessly.
This functionality is embedded in qualified SmartArray servers controllers (SA6i, SA642). Therefore this requirement exists to connect MSA500 to SA controllers, not to simple SCSI.

Re: MSA500, 4 Servers, redundant controller

Gerald Hochegger — Thu, 17 Nov 2005 05:31:12 GMT

Thanks Basil,

after reading MSA 500 G2 technology white paper (page 6) I would also think a
seamless failover is possible, when you are
using SA6i, SA642 HBA's.

But everyone I asked so far said:
* I'm not sure if it really works
* Maybe it works only with the
HP Multipath software on the Servers
* The failover takes very long
(about 30 seconds or more)

Do you have any experience with such a
configuration ?

Re: MSA500, 4 Servers, redundant controller

Jacob Zeeman — Thu, 17 Nov 2005 17:15:51 GMT

Hi Gerald,

Basil is correct. The controller will fail-over automatically and the servers should not lose connection to storage.
However you will need some kind of control in place so that only one server is access a particular logical drive at a time. Whether you have a clustering service set-up, or are using the Selective Storage presentation that comes with the HP ProLiant Array Configuration Utilty, you must have some kind of control mechanism configured.

As for Multi-path, this software merely allows for redundant controller fail-over in the server. It has nothing to do with the redundant controllers in the MSA500.

Hope this helps.

Jacob Zeeman
HP Server Storage Specialist

Re: MSA500, 4 Servers, redundant controller

Gerald Hochegger — Thu, 17 Nov 2005 17:51:58 GMT

Hello Jacob,

your explanations helped me a lot.

I'll buy MSA 500 with the 4-port I/O Module
and a redundant controller.

Our setup is "clustered" - all 4 Servers
normaly run their own Linux Vservers
(http://linux-vserver.org)
from partitions of the MSA Array.

If one Server fails (heartbeat), his peer
cuts him the power connection (with ILO over ssh), mounts his Vserver partitions from
the MSA Array and starts his Vservers.

This works quite reliable, but a controller
failure on the MSA 500 would bring down all
4 Servers. With a working controller failover
on the MSA 500, I can eliminate this single
point of failure.