You only need to prefer traffic if you are getting congestion.
If your storage network is experiencing network congestion, you should provision more bandwidth or a better switch.
So the real answer is to provision enough bandwidth so congestion doesn't occur.
The literal answer though, is: QoS.
If the requirement is for all traffic between the two devices, you could simply use a source-port classifier:
(So I'm assuming you have a 4-port LAG to each device, eg, Trk1=C2,C3,D2,D3; Trk2=C4,C5,D4,D5)
interface C2-C5,D2-D5 qos priority 3 [Layer2 QoS}
interface C2-C4,D2-D5 qos dscp 000011 [Layer3 QoS]
Otherwise, if there is some traffic from those devices that needs priority and some that doesn't, you need to classify it, eg:
class ipv4 PriorityAppsClass
10 match ip 10.100.10.40 10.100.20.30
20 match vlan 210
policy qos PriorityAppsPolicy
class ipv4 PriorityAppsClass action ip-precedence 3 action dscp 000011
default-class action ip-precedence 0 action dscp 000000
interface Trk1,Trk2 service-policy PriorityAppsPolicy in
*** This isn't working config, this is just me typing stuff in - you will have to refer to the Advanced Traffic Management Guide for your switch model for correct syntax
*** Frequently, I see people who do this stuff go, "oh, 7 is the highest priority, I'll use that". Don't be retarded like them. 7 is not for you to use.
7 is for internal switch processes to use (eg routing protocols)
6 is normally (ie, as per the RFC) similarly reserved, but in HP-land, 6 is (mis-)used for Voice.
5 is normally voice - if you have a mixed-vendor network, you should definitely use 5 for voice. That will involve re-mapping anything generated by HP (eg Voice VLAN) (qos dscp-map 000101 priority 5). So this is low-bandwidth, low latency traffic
4 is for high-bandwidth, low-latency traffic - video.
3,2,1,0 are for your apps. By default, usually 70% of the switch buffer memory is allocated for 0 and 3, because it is expected that you will have most of your bulk data going through as default priority (0) or if prioritised, as 3. Your storage traffic should definitely be 3.
