I’ve been wrestling with a couple of architecture issues over the last few weeks. They are interlinked; but stand alone as separate issues.
First is three datacentre. So imagine a scenario where there is a normal datacentre pair, reasonably close to each other. New rules require another datacentre some distance away, which will be out of zone. This means a distance of perhaps 50 or 60 miles. The original datacentre pair were only 5 miles apart. The aim is to be able to replicate between the local pair with a third copy in the remote centre. Not a problem you might say; the local pair can be synchronously replicated, the remote copy can be async. Well, OK, that would work and the major array vendors can do that today. But….I really don’t want async and I don’t necessarily want to pay for three copies.
How can I do it? At the moment I don’t think it is possible; certainly I need to still have three copies and I can’t reduce the replication to the remote site to synchronous without incurring a penalty. There is a possible scenario using a USP to virtualise the disks at the remote site to one of the local sites however this may not provide suitable data integrity.
I’d like to see the vendors provide this solution; in fact I think the best place for this requirement to be implemented is within the SAN as part of a director. I don’t think any vendors are working to develop this; if they are they’d be cutting into the storage array vendors patch, something that might not be too popular.
In case anyone decides to comment, I am aware of EMC InVista but I don’t think it offers this degree of functionality and flexibility.