Port Speed

[ehuang]

A quick and easy question:

On my Storageworks SAN FC Switch 4/32, I see different port speed settings. 2, 4, N2, and N4. 2 and 4 stands for 2Gb/s and 4Gb/s, what is "N2" and "N4"?

Thanks.

[marsh_1 · Accepted solution]

hi,

you can either set the speed 2 or 4 or set it to negotiate the speed 2gb or 4gb (n2 and n4 respectively)

hth

[IBaltay]

Hi,
the speed can be fixed (1, 2, 4, 8) or negotiated (N1, N2, N4, N8, or AN - autonegotiated)

[ehuang]

Would N2 better than 2 (or vice versa) if the max speed on the device is known a certain 2G?

[marsh_1]

hi,

only set the port to negotiate if the hba at the other end supports negotiation otherwise hard set the speed, most newer hbas support negotiation.

hth

[IBaltay]

maybe the SAN performance consideration section (from page 157) of

http://h20000.www2.hp.com/bc/docs/support/SupportManual/c00403562/c00403562.pdf?jumpid=reg_R1002_USEN

could help you here

[ehuang]

thanks guys. do i have performance issue if i set the speed on the device end as "auto" but the swtich end as "n2" or "2" instead of "an"?

[marsh_1]

hi,

a lot of this is a mix of personal preference and some manufacturer recommendations, some people prefer to hard set the speeds to save the negotiation time when the link comes up, a number of the manufacturers of the hbas/switches recommend auto both ends, while the link is up there is no difference.

hth

[ehuang]

question answered.