Fibre Channel (SAN)

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Occasional Contributor
Posts: 9
Registered: ‎02-26-2009

Disabling ISL links question ..

We've got two Brocade 48K directors connected at two sites for inter-site DR. We will be switching off one of the sites completely (for electrical work).

Is it recommended that for the duration of the site power-down we should disable all inter-site ISL links to prevent errors being logged ?

Note: we use ISL trunking for the ISLs.

All equipment in the one site will be powered off for the duration.

thanks.

Valued Contributor
Posts: 931
Registered: ‎12-30-2009

Re: Disabling ISL links question ..

Depending on how big your site is, I would disable the ISL to the DR site prior to anything being shutdown and after any replicatin has been paused/halted/stopped.

Reason being that components that shutdown cause RSCN's in the fabric's

By shutting the ISL first (which will cause RCSN as the other site drops off) you won't get the RSCN's in your still working site.

Perhaps as a precaution make your principal switch the one thats not being shutdown.

After maintanance i would first bring up the switches and storage, then restore ISL and after that startup other componenten.

Occasional Contributor
Posts: 9
Registered: ‎02-26-2009

Re: Disabling ISL links question ..

thanks, your answer is on the same lines i was thinking. Which end would you say to disable the ISL links at, the one being power down, the one staying live, or both ? Making the principal the one that's remaining live makes good sense.

thanks.

Valued Contributor
Posts: 931
Registered: ‎12-30-2009

Re: Disabling ISL links question ..

Disable on the live one.

The one being shutdown is an option but you'll have te make sure its persistenly disabled.

Otherwise it would become online after power-on which you want eventually but then you won'be in control.

To recap your choices:

-disable on the live switch (persistent or not makes near as no defference)

-disable on other switch make sure its persistent

If you don't make the active one principal it will happen automaticlly when yhe ISL go down, but again you're not in control.

Occasional Contributor
Posts: 9
Registered: ‎02-26-2009

Re: Disabling ISL links question ..

thanks.. i've marked and closed this as the correct answer..

Super Contributor
Posts: 635
Registered: ‎04-12-2010

Re: Disabling ISL links question ..

Hi,

live is not black or white.

I would answer the question contray.

Answer your self following question.

Do you shutdown the servers before you switch of the power?

Did you have device let say server which are located  on your "power off site" and they have storage on the other side?

Do you have storage replication between both building?

Do you have host based mirrors which are copying data to the other side?

If one or all questions are answered with yes you should shutdown your switches after all servers and storage arrays are down. Give all device the possibility to close there connections.

You will receive RSCN anyway because you will loose all device from one side. Make sure that not all device disapear from fabric at the same time.

I would say shutdown all devices (Server and storage)

after that I would run the command switchdisable on the power off side. After that I would disable the ISL ports on the other switch for safty reason.

After you had done your shutdown on the SAN switch your network team can switch off the ethernet.

Power on will be done in that way.

1.) power on the switch

2.) run switchenable command

3.) enable ISL port

4.) power on storage arrays and check it carefully

5.) Power on the servers.

Do not change during the power off state your zoning DB otherwise you will get a segmentation.

I run this process two or three times without any pain.

I hope this helps,

Andreas

Occasional Contributor
Posts: 9
Registered: ‎02-26-2009

Re: Disabling ISL links question ..

thankyou for your answer, but i fail to understand how RSCN can be propogated to the other side if i disable the ISL links at both sites !

e.g. SiteA being shutdown.  SiteB staying up.

I can understand that i will get RSCN, on switch at siteA, from any servers on siteA trying to access any storage on SiteB, but if the ISLs have been disables surely they will be localised to the now unlinked siteA switch ?

SiteA and siteB have identical storage and identical cluster nodes for all services at both sites, therefore when siteA is switched off all that is going to happen is clusters will run at half capacity (half the normal max nodes) but storage will be unaffected. We've ensured all hardware mirroring primaries are on siteB and software mirroring will be made to only access siteB storage for the duration.

I have a plan on how to proceed now, thanks all who contributed.

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