VPLEX Metro Questions

Hi,

Can you elaborate the question ?

it depends on what hosts are connected to which cluster and how is it zoned.

BR,

Sameer

It sounds like you are using a host cluster (is this local to a site or across sites like a geographically dispersed cluster?).

Assuming a geo-cluster and the usage of distributed volumes within your VPLEX metro, the I/O from the clustered hosts at each site will go to the VPLEX distributed volumes and not the arrays comprising those distributed devices directly. A VPLEX distributed device is comprised of 2 legs - a device from an array at each site. This distributed volume is then presented to your hosts as a logical single LUN that both sites can see and write to, so you are writing to the VPLEX virtual volume and not the underlying devices that comprise that distributed volume.

As a flow of I/O, unless setup in a cross-connected environment, the pathing at each site will likely have your hosts zoned to the local VPLEX's Front-End directors. This means that when you perform I/O's, it will hit the VPLEX distributed volumes and in the case of writes be written through to that sites local array FIRST, and then replicated over the VPLEX WAN to the other sites array (the other leg of your RAID-1 Distributed device) before an acknowledgement is sent back to the host.

So in terms of your question, the clusters are likely writing through to their local array first, but they don't write to a specific site only....they write-through locally and have that write mirrored through the VPLEX WAN to the other site before any host acknowledgement is received. In a cross-connected environment, it could be possible that you are writing across the sites initially I guess, but that would be rare since products like PowerPath will chose the fastest path and unless you have path failures or degredations, that will likely always be your local site. But again, you didn't mention cross-connect so we cna probably strike it from this conversation.

HTH

For example in the distributed volumes within the VPLEX metro, in the event of the performance issue, how can we know which is the array the vplex is reading the data from (the DR or the production), using the VPLEX gui or cli?

The best way I have found to determine which cluster the host(s) is writing to is to look in Powerpath on the host side (Microsoft Server) inside of PowerPath when you expand the disk section it will show you the SN of the VPLEX that you are writing to. If you are using AutoStandby (trigger=prox) for your policy of the DD then you can expand each volume in PowerPath and see which path are active and which path are in (asb:prox). 

From a VPLEX perspective, if you have a cluster separation due to WAN-COM issues or VPN issues you can go to that DD and show the map of that volume and it will show you what cluster that DD is writing.  If you do not have Witness and are using CG rule sets then that will dictate where the DD goes in the event of a cluster failure. 

Thanks,

AM