DCB warning on EQL PS6210x

Question

Hi, i was facing a DCB warnings on a PS6210XV connected to a M1000e chassis - M8024-K switch. warnings disappeared from the EQL interface after disabling DCB on the switch. can someone explain why DCB is reporting alerts when enabled, while unless i am mistaken DCB is recommended to be used in such a situation ethernet traffic for data and storage. my knowledge in storage and networking are so limitted in case my question looks dump but i appreciate getting an answer.

dwilliam62 · Answer

Hello, It is not a dumb question at all! By spec, devices that support DCB advertise to the network switch that they do. If you are familiar with Fibre Channel it works in similar way. The switch is in charge and devices attached follow its lead. Do the EQL array just says I am read for DCB if enabled. The switch had it enabled but not configured. So the EQL detects that and reports the error. When DCB is enabled on switch, traditional flowcontrol is disabled in favor of Preferred Flow Control from DCB. But if DCB isn't configured then neither congestion management is available. DCB is designed for locations where ISCSI and NON iSCSI are mixed. When you have dedicated switches or at least segmented then there is no need for DCB. You also need iSCSI initiators that support DCB. Which usually means dedicated iSCSI HW cards. Regards, Don

Origin3k · Answer

Cant speak for M8024-K but we have the PC8024F and it have DCB just on paper and nothing something which is compatible to the EQL requirements. I cant remember if EQL comes with DCB support from the beginning but IIRC is comes with a later FW upgrade. Disable it on the switchport and youre fine.

If you have dedicated ports in use for iscsi i cant see any benefit and also IIRC there is no general support from vSphere ESXi. If you take a look there is only one single KB and its referer to a custom DELL solution.

Regards,
Joerg

dwilliam62 · Answer

Hello Joerg,

re: DCB. On EQL support is based on Firmware level and array must be 10GbE.

re: 8024. DCB was first only for FCoE. Which requires DCB, you can't use it without DCB being configured. When iSCSI was included additional features of DCB were required. Called TLV and PFC. These required additional HW that the 8024 and Cisco 5000 series didn't have. So DCB for iSCSI is not supported on those switches. The switches still announce "DCB" support. Which the EQL responds to as any DCB capable device is expected to.

Re: ESXi. The SW iSCSI adapter does not support DCB, but there have been H/W cards that do for sometime. That KB was from very early on before these cards were generally available. Now they are in the VMware HCL.

Regards,

Don

EqualLogic

DCB warning on EQL PS6210x

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