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Brocade switch "roles"
Hi all, I just recently extended our switch fabrics by adding a couple of Brocade DS4100B 32 port switches to our 2 Brocade ED12000B's. Prior to the addition of the DS4100's my original switch was the principal. With the new 4100's added in they are showing as principal. Is it because the DS4100's are newer faster or higher code? Is there any issue with this? I don't see anything out of the ordinary but you know how that can sometimes come back and bite you....thanks....mack
sysmgr1
128 Posts
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November 30th, 2006 14:00
GlenH
141 Posts
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November 30th, 2006 19:00
The principal switch election process is quite straight forward:
Any time a new switch joins the fabric, a principal switch election will occur.
The principal switch is elected based on 2 things.
1. The switch priority (ie: a switch definitely does wish to be principal). If only one switch wants to be principal, then it wins the election.
2. The WWN of the switch. If multiple switches have equal priority, then the switch with the lowest switch WWN will become the principal.
It is highly recommended with a large fabric in a core-edge topology that you make the core switch the principal as the principal switch must communicate with all other switches in the fabric for routing and fabric events. Selecting an edge switch as principal will place un-necessary Class F traffic on the ISL's connecting to the core.
For small/mesh fabrics, it is less important who holds the principal switch role.
It's also a good practice to make zoning and configuration changes from the core/principal switch.
For brocade, you can use the "fabricprincipal" command to set the switch priority.
There is some additional information on fabric design and principal switch elections in the EMC Networked Storage Topology Guide which is available from Powerlink.
Just one further note - the principal switch election process has nothing to do with the domain ID of the switch (for some reason many people seem to think these are linked)
Good Luck,
Glen
mack-xwWos
21 Posts
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December 1st, 2006 10:00
sysmgr1
128 Posts
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December 1st, 2006 12:00
It makes no difference if you do zoning changes from the primary switch or any other switches. It makes no difference as to what switch is principal or subordinate.
GlenH
141 Posts
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December 3rd, 2006 16:00
You must have found an old link as that guide is updated regularly (Most recently July 2006) - try here:
https://elabnavigator.emc.com/emcpubs/esn-topo/wwhelp/wwhimpl/java/html/wwhelp.htm
It has a number of references on principal switch placement, but this probably sums them up best:
" One switch in the fabric is responsible for the distribution of domain IDs, and plays a role in the route creation for fabric management traffic. This switch is known as the principal switch. Since this switch must communicate with all other switches and is the basis for fabric traffic routing, this switch should be centrally located. This will assist in the uniform delivery of information in the fabric, and provide a consistent response to fabric build events. "
The document does have a slight error however where it says the following:
" Connectrix M-series switches have the ability to set a switch priority. EMC recommends that you set selected M-series switches to Always based on their location in the fabric. Connectrix B-series switches do not provide a mechanism to set the switch priority. EMC recommends that the B-series switches with the lowest WWNs always be located at the center of the fabric. "
Which of course is out-of-date as the fabricprincipal command can now be used for the B-series switches... I've sent a note for the doc to be updated.
Brocade make similar recommendations and also recommend that the core switch be the designated mangement switch in their brocade SAN designer certification study guide here:
https://www.brocade.com/education_services/pdf/BCSDNutshell-Apr05.pdf
Glen.
JasonBailey
147 Posts
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December 3rd, 2006 17:00
little sense concerning the switch roles. It makes no
basis to the fact that it has any real affect on
performance. The current Brocade publications on SAN
design make NO reference to the principal/subordinate
roles as being relevant or affecting performance..
Brocade SilkWorm. Design, Deployment, and. Management Guide. SAN DDM. Version 3.0
http://www.brocadejapan.com/resources/tl/pdf/DDM_v3_0_53-0000366-03_C.pdf
page 127:
For Core/Edge topologies, the principal switch should be a core switch for optimal fabric operation. If using a SilkWorm 12000 or 24000 in the core, utilize it as the principal, as it has the greatest availability.
the primary switch or any other switches. It makes no
difference as to what switch is principal or
subordinate.
page 92:
It is important that the SAN administration team select one switch in the fabric as the administration switch. Using one switch for access lessens the possibility of multiple administrators making changes to different switches in the fabric at the same time.
Keeping in line with the terminology used by Secure Fabric OS, this switch is termed the primary management switch.
There are several reasons to select the core switch as the primary management switch for zoning, time services, Fabric Manager, Web Tools, and general administrative access.
The core switch is optimally located to communicate with all other switches in the fabric. The core switch is commonly the larger switch with a more powerful control processor. When zoning information is propagated, the switch where the zone
information changed is responsible for distributing the zone information to all other switches in the fabric. The core switch is directly connected to all other switches in the fabric.
sysmgr1
128 Posts
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December 4th, 2006 08:00
Bottom line, if it makes you happy, go ahead and set it.