ProCurve network expansion

I've hit a bit of a wall with our network scale-out. As it stands right now:

We have five ProCurve 2910al switches connected as above, but with 10GbE connections (two CX4, two fiber). This fully populates the central switch above, there will be no more 10GbE Ethernet connections from that device. This group of switches is not stacked (no stack directive).

Sometime in the next two or three months I'll need to add a sixth, and I'm not sure how deep of a hole I'm in. Ideally I'd replace the core switch with something more capable and has more 10GbE ports. However, that's a major outage and that requires special scheduling.

The two edge switches connected via fiber have dual-port 10GbE cards in them, so I could physically put another switch on the far end of one of those. I don't know how much of a good or bad idea that would be though.

Is that too many segments between end-points?

Some config-excerpts:

Running configuration:

; J9147A Configuration Editor; Created on release #W.14.49

hostname "REDACTED-SW01" 
time timezone 120 
module 1 type J9147A 
module 2 type J9008A 
module 3 type J9149A 
no stack

trunk B1 Trk3 Trunk 
trunk B2 Trk4 Trunk 
trunk A1 Trk11 Trunk 
trunk A2 Trk12 Trunk 

vlan 15 
   name "VM-MGMT" 
   untagged Trk2,Trk5,Trk7 
   ip helper-address 10.1.10.4 
   ip address 10.1.11.1 255.255.255.0 
   tagged 37-40,Trk3-Trk4,Trk11-Trk12 
   jumbo 
   ip proxy-arp 
   exit 

Solution 1:

I would just switch to having two core switches instead of one. The two core switches would be connected by 10GbE, leaving six available 10GbE ports on core switches. That would support adding up to 6 additional edge switches. Your network diameter only increases by one, which is clearly the minimum possible.

If your switches support trunking, you could use a 2x10GbE link to trunk the switches. That would leave you with 2 10GbE ports left on each switch. That will work with just six switches but you'll be back at a wall if you ever need another switch.