Network Challenges with SAN Replication

Unanswered Question
Jun 28th, 2010

Hi, although this question involves SAN replication between 2 data centers, the nature of my concerns are with regard to the networking component of it.

My question is broad based because I havent had the conversation with the client yet.

My question is: What are the network-oriented concerns when implementing a SAN replication solution? What are the possible issues and challenges that one should be aware of?

I can think of two right off the bat -- available bandwidth and QoS...but I would liek for someone to expand on this. Also, what are other concers?

Thanks

Victor

I have this problem too.
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Jerry Ye Mon, 06/28/2010 - 10:12

What kind of SAN replication? FCoE or native FC (DWDM)?

If it is FCoE, you will have to put into consideration of extending L2 domain across your WAN, which can be tricky with QoS.

Regards,

jerry

lamav Mon, 06/28/2010 - 10:28

Hi, thanks for responding..

It is an iSCSI SAN -- probably asynchronous -- replication environment, using Dell EqualLogic arrays. So, the need for L2 adjacency between SAN arrays is not there...

what else comes to mind? How would you approach the implementation of this solution from a network perspective?

Thanks

Roland.Corbet Tue, 06/29/2010 - 09:58

Hi,


I'm not sure I have an answer, however, we're currently in the planning stages of a similar project ourselves, so I thought I'd share our thinking...

We're looking to deploy two Dell EQL arrays at two separate locations, with traffic going across the Internet.

We're planning on using the following kit:

10mbps connection to Internet via leased line.

Cisco ASA 5510 Firewall at each site.

2 x Dell PowerConnet 6224s at each site (to support high availability.  We should probably have 2x ASAs at each end too, but as always cost is a limiting factor!)

The basic configuration we have planned is:

Servers connect to Dell PE 6224

6224 defines separate iSCSI VLANs at each location

ASA 5510s form a VPN tunnel across the internet and provide transport for VLAN traffic between sites.

6224s configured to do L3 routing and send traffic to ASA 5510s as default gateway, thus traffic for a subnet/VLAN at the other site should flow over VPN tunnel.

In terms of a basic set-up, we think this is all that is needed to have the SANs at two sites talk to each other.

We may then look at the QoS on the ASA 5510s at each end to ensure that SAN traffic gets priority over internet traffic at each site in some way - e.g. guarantee a minimum of 6 of the 10 megabits etc for SAN replication.  We've not quite bottomed this part out yet.

Hopefully our ideas may be of some help.

I'd welcome feedback on our plans too, if anyone wishes to comment.

Roland

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