FW 7.0.2 - Synrep Issues and Errors

The connection between the SAN's is configured as followed:

- Single Cisco Redundant stacked switch between the SAN's

- MTU 9000

- 1-4 Gb/s

Type: 2x PS4000 and 2x PS6100 where the sync rep is only on the same type (4000 -> 4000 and 6100 -> 6100)

depending on the type of equallogic, it has 2x1Gb/s interfaces or 4x1Gb/s interfaces to the switch.

Cisco C3750E

no one?

Please check if the upgrade to v7 somehow enabled DCB if it was disabled before the upgrade. If you find it enabled, please diable it (only possible via CLI, not via GUI with v7).

Let us know if that helped.

Best regards, Joerg

Don: Please clarify.

Many switches will turn off any flow control if you disable dcb on the switch side. Thus - please explain.

Why am i not to disable DCB on the array side, ever? That does not make any sense to me, because a) it was possible for a long time from within the gui and b) maybe you don´t want to disable it on the switch side for several reasons but you need to disable it on the array because the initiator don´t supports it. Also, i often spoke to EQL techs who told me where to disable it on the cli side for exatly that reason. Also, it is clearly explained in the cli guide. So i am concerned now: Is there *anything* we should know about that and why do you explicitly mention it?

I had a coincidental chat about that with EQL techs in frankfurt/germany last week during the dell enterprise forum and it was exactly about dcb and how dcb is not widely supported by initiators, especially s/w initiators and how to disable it on the array level.

Don maybe you remember this we had a conversation in this forum about a year ago on exactly the same topic - but you never told me why it is so important to you to explicitly not disable it an the array level?

I really want to know the reason because if there is something important i should know about that i´d like to understand that and disable it on the switch side instead of the array side. But as far as i know and also as far as my friends and colleagues in frankfurt are telling me, disabling dcb on the array side does no harm at all. Please clarify.

Best regards,

Joerg

Hi Don,

OK, thanks. Could you talk to engineering for the reason for telling you this? Please do me the favor because the enginners i myself talked to, told me otherwise.

Second, please give exact advise how to disable DCB on a DELL 8164 (now N4064) so that it´s really disabled while in parallel keep link layer flow control *fully* intact. Because i don´t know how to realize that.

Best regards,

Joerg

@Pentium3nl:

I don´t think STP/RSTP is your *real* problem. If it helps to disable STP on these ports you are either confronted with a) many global (r)stp recalculations or b) a flappy connection which goes online and offline from time to time. Both things are not good and the real reason should be your target. So i suggest to keep looking for possible causers of a) or b).

@ Don:

Thanks, Don.

I still see absolutely no advantage in turning DCB globally off on switch side. On the array, however, i can do it "on the fly" without the slightest kind of disruption. Again, i am wondering why you removed it from the GUI with V7. I would change that back if i could. But then again, sadly i can´t ;-) I can only suggest.

Best regards,

Joerg

PS by the way, am i the only one who finds these lines at least a little bit scary ->

Hi Don,

i am completely with you on that point. BUT to use DCB in real world, you have to make sure, that a) EVERY switch in the line of traffic EQL-to-initiator carries and supports DCB, b) every target can use DCB and c) every initiator can use DCB. Now let´s say a fresh EQL Version 7 comes to the network, it is attached to a fresh n4064 and thus automatically enables DCB and thus, uses PFC. After the N4064 there are other switches, let´s say some 8024s and others WITHOUT DCB enabled. What will happen? The EQL will enable DCB because it talks to the N4064, but the afterlying switches don´t and the initiatitor don´t, too. So - we find ourselfes in a bad scenario because what i (the user) want is at least flow control. Yes, i agree, pfc would be nice -  but let´s be honest - there are not many initiators in real world at this point which do fully support it.

So - what now? Either I am forced to do a *very* hard modification to my N4064s (which will break network connectivity by the way, just read the intructions i posted earlier) OR i can set DCB off on the CLI of the EQL with Version 7.

Again, i would set this off on the EQL array. At least while DCB is let´s say *in the beginning* state, especially when it comes to the *whole* ecosystem, in detail the initiators.

Best regards,

Joerg

If you don't and just disable on the array, then in a DCB environment that traffic ends up in the lossy queue and no link layer flowcontrol as a backup.   Which can result in terrible performance and connection drops.

For a 8164/N4064 i don´t believe that is correct. The 8164 factory design (standard config) is preconfigured to respond to DCB and EQLs will select and use DCB. But the 8164 (factory design) has also traditional flow control enabled and will respond to it and use it. I can confirm a 6210S with dcb disabled via CLI connected to a factory standard 8164 behaves perfect, uses flowcontrol and has no connection drops or performance problems. In fact, we did quite a few nasty benchmarks with it and it performed really well.

Now another word regarding "DCB environments" and "the other end of the line". I am not aware of many s/w initiators which really support dcb. So if you don´t use dependent initiators - you probably will not be able to use dcb in many cases.

Best regards,
Joerg

Yes, that is only one adapter. In my opinion a quite remarkable reason for enabling DCB as default in your switches and also in your storage arrays. Because DCB is *always* end to end. And as there is not many on the initiator end this time...

My personal opinion: You would have less problems (at this very time - the future is another thing, i am sure the future is DCB) making it easier to disable DCB or disable it per default and make it explicitly "activatable".

But so - i guess there is no way i can convince you to reconsider the DCB default activation in your switches and/or your storage arrays ;-)

Best regards,

Joerg

Hi Don,

i absolutely agree with you. But guess what the switch vendors are saying? "Hey - we got a super duper switch which is ready for everything - dcb, traditional flow control - we got it all setup for you ;-). Just plug it in and you are on, whatever you wish, our switch does it out of the box ;-)"

To be honest: This won´t change. Really.- Even DELL does it. Everyone does it. And i got used to it.

So i won´t change my point of view ;-) - I would want an easy way to disable dcb on the endpoint.

Best regards,

Joerg