Rebalance Gateway Connections

[Bart_Heungens]

You have a good point there. The FOM is there to decide which site must stay active in case of a split-brain situation on the network.

If you want to move the FOM to the first site, you can remove the FOM and start the manager on the third storage node... Result would be the same then...

[jpiscaer]

That's exactly what I'm thinking: if the FOM is in the same site, there's no need for it anymore, just start a third manager in the primary site.

[jpiscaer]

Can you inform me wether your systems (ESXi-servers) are grouped into sites, or not? I suspect your servers aren't grouped into a site, thus SAN/iQ has no idea that it needs to rebalance the Gateway Connections.

[Bart_Heungens]

It depends from customer to customer... Some want site-aware servers, some others not... Performance versus high availability... A lot depends of the ISL between the sites...

Kr,

Bart

[jpiscaer]

I'm still struggling with what the Gateway Connections actually do in a Multi-Site SAN with site-affinity for ESXi-hosts.

An ESXi-host connects to the cluster's Virtual IP and gets redirected to one of the storage nodes. You can see which storage node a host connects to for each volume by viewing the Gateway Connection. Each volume is accessed through the same storage node, so all hosts connecting to a volume show the same Gateway Connection.

What other implications does the Gateway Connection have when connecting ESXi-hosts in a Multi-Site SAN (single Virtual IP, two sites)?

[Bart_Heungens]

If the servers are site aware they should connect to a node (with a manager running) in their specific site.

If the servers are not site aware they should connect to all nodes available...

My test/demo setup is currently single site so I cannot validate this though... If I have the occasion I will take a deeper look at it...

Kr,

Bart

[jpiscaer]

If hosts are site-aware, they connect to nodes in the same site; but does each host connect to a single storage node for a given volume?
In other words, does a host connect to multiple hosts for a single volume?

[Bart_Heungens]

If you install the MPIO DSM (currently available only for Windows) then yes the server will connect to all available storage nodes... If the MPIO DSM is not installed it will connect through the VIP...

Since the MPIO DSM does not exist yet for ESX, the only way to get the best performance is to create multiple VMkernel ports and bind them to the vmhba following the procedure that is already often mentioned here on the forums. Command line stuff in ESX4, via the GUI in ESX5...

Kr,

Bart

[jpiscaer]

yeah, not having a DSM for ESXi is a real downer at the moment.

I did a test this week: the storage node that is the Gateway Connection for a volume handles *all* I/O to/from the ESXi-host. The storage node will communicate with other storage nodes on the back-end to fetch / write blocks. This limits the maximum performance of a single volume to the maximum performance of a storage node. Because SAN/iQ assigns Gateway Connections to as much storage nodes as possible, this will load balance a bit, but it's a non-optimal configuration.

HP needs to release a DSM (or MPP) for ESXi to get performance for a vSphere environment on par with a Windows environment.