Hi,
On a pair of Switches deployed in VSF a single logical VSF Port should be used, on that single VSF Port one or more (generally up to physical interfaces can be aggregated...if you have aggregated two interfaces with, each one, a speed of 10Gbps - SFP+ case - then the VSF link bandwidth is the sum of single speed so 10Gbps+10Gbps=20Gbps.
On a KB.16.05.0007 note how the output of show vsf command, the VSF Port Speed references to the single interface speed and not about the aggregate speed (bandwidth):
VSF# show vsf link
VSF Member 1
Link Peer Peer
Link Link-Name State Member Link
---- ---------- -------- ------ ----
1 I-Link1_1 Up 2 1
VSF Member 2
Link Link-Name State Member Link
---- ---------- -------- ------ ----
1 I-Link2_1 Up 1 1
VSF# show vsf
VSF Domain ID : 1
MAC Address : f40343-XXXXXX
VSF Topology : Chain
VSF Status : Active
Uptime : 403d 19h 11m
VSF MAD : OOBM
VSF Port Speed : 10G
Software Version : KB.16.05.0007
Mbr
ID MAC Address Model Pri Status
--- ----------------- ------------------------------------- --- ---------------
1 f40343-XXXXXX HP J9850A Switch 5406Rzl2 255 Commander
2 f40343-XXXXXX HP J9850A Switch 5406Rzl2 128 Standby
To see the bandwidth you should issue the show vsf link utilization command:
VSF# show vsf link detail
VSF Member: 1 Link: 1
Port State
-------- ------------
1/C7 Up: Connected to port 2/C7
1/C8 Up: Connected to port 2/C8
VSF Member: 2 Link: 1
Port State
-------- ------------
2/C7 Up: Connected to port 1/C7
2/C8 Up: Connected to port 1/C8
VSF# show vsf link utilization
VSF Link Utilization:
Link Average Link
Member Link Bandwidth Utilization %
Rx Tx
------ ---- --------- ----- -----
1 1 20G 0 0
2 1 20G 0 0