High Availibility Configuration

[Vincent Farrugia]

Hello,

We are soon implementing a HA configuration between two rp5450s and 2 SC10s. This will be done using ServiceGuard of course.

Each server has 2 Dual Port SCSI PCI cards. Attached please find our suggested configuration. Please tell us any comments, what is good/bad etc. Take into account that the dual SCSI cards are SPOFs i.e. it is different from having 4 single SCSI cards.

The numbers shown are the SCSI IDs. Below please find the legend.

SA1AM = Server A SC10 1 Alternate Mirror
SA2P = Server A SC10 2 Primary
SA1PM = Server A SC10 1 Primary Mirror
SA2AP = Server A SC10 2 Alternate Primary
SB2PM = Server B SC10 2 Primary Mirror
SB1P = Server B SC10 1 Primary
SB1AP = Server B SC10 1 Alternate Primary
SB2AM = Server B SC10 2 Alternate Mirror

Thanks,
Vince

[John Palmer · Accepted solution]

Hi Vince,

Your proposed hardware setup looks OK to me. We've had a couple of similar configurations running for some time.

I presume that you intend to mirror between the two SC10's?

I don't agree that the dual SCSI cards are SPOF's, true you'd get a double failure but you still have access to both SC10's via the other card. They're very reliable in any case.

Regards,
John

[Steve Lewis]

I had a look at your configuration (nice diagram!) and have this to say:

Make sure that you mirror each primary lvol to the other SC10 from the other controller card on each server.
E.g. lvolx prim from card1 port 1 -> SC10a
lvolx mirror from card2 port 1 -> SC10b

lvoly prim from card1 port 2 -> SC10a
lvoly mirror from card2 port 2 -> SC10b

The secondary server would have an identical configuration, plugged into the other end of each SC10.

Currently you appear to be mirroring to the same SC10 from the other controller (correct me if I am mis-understood the naming). This would create a potential SPOF if an SC10 went. I know they have 2 power supplies but that may not be enough.

The other method is to install a PAIR of FC controllers inbetween to allow for expansion and greater distance between the servers. You may want to put a large gap between the servers in case of disaster to the whole site, which would require fibre.

[Tom Geudens]

Hi Vincent,
Boy, am I jealous ... two SC10 racks :-). We have a very similar configuration, using only one SC10 rack (+A500 +OPS). We've got > 70 of those configurations running already (and going for 160). We tested this with L2000's too and those are a lot more stable (but too expensive) so I think that part of the your configuration is sound.

I'm very curious as to your networking. We've got two switches and three network connections on both servers (using an extra combo card) which allows us to create three paths between the servers.

Regards,
Tom

[Vincent Farrugia]

We have 2 4-port 10-100 NIC cards on each server (8 in all). Unfortunately, we have only 1 12-port Procurve switch on which we can connect to. But the customer will source an extra switch soon so as to not have any SPOFs.

Thanks guys, any other input is welcome, I'll assign points later.

Vince

[Vincent Farrugia]

Sorry that should be 1 4-port NIC on each server :-)

[Vincent Farrugia]

And, yes, I forgot to say... the SC10s are mirrored between each other.

[Duncan Edmonstone]

Vincent,

I'm assuming you will be using Physical Volume Groups to maintain your HA disk configuration yes?

Assuming you are, and you are also considering using EMS HA monitors with MCSG you should make sure you follow the rules defined in the the HA monitors manual...

http://docs.hp.com/hpux/onlinedocs/B5736-90025/B5736-90025.html

HTH

Duncan