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Redundancy iSCSI SAN networking

Posted on 2013-01-18
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Last Modified: 2013-01-25
Hi;

I am using EqualLogic iSCSI SAN with VMWare in office.  My configuration like this..

2 x 10Gbps LAN switch as iSCSI SAN / LAN core switch (these 2 switches are stacked each other)

I have two VLAN configured in the iSCSI switch, VLAN10 and VLAN20.

VLAN10 is for iSCSI SAN connect to EqualLogic
VLAN20 is for LAN connect to Server and the other LAN switches.

These two switches provides 48 ports (24 ports each).
On iSW1, port 1 - port 14 assigned to vlan10 and port 15 to port 24 assigned to vlan20
On iSW2, port 1 - port 14 assigned to vlan10 and port 15 to port 24 assigned to vlan20

All VMs are on VLAN20, (192.168.0.x)
VLAN10 is for storage network. (10.0.0.x)

Port 22,23,24 on iSW1 and iSW2 are used to connect to another 3 LAN switch (LAG Group)

iSW1/22 <--> SW3/44
iSW1/23 <--> SW4/G2
iSW1/24 <--> SW5/G2

iSW2/22 <--> SW3/43
iSW2/23 <--> SW4/G1
iSW2/24 <--> SW5/G1

SW3, SW4, and SW5 are for LAN which are all workstation and other network equipment.

I found that if I turned off iSW2, I can still able to connect all hosts in VMware VMs but if I turn off iSW1, I cannot access to all hosts in VMware VMs which do not provide me the redundancy expectation.

Each VM host has redundancy NIC connect to iSW1 and iSW2.

any wrong with this configuration?
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Question by:KANEWONG
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Expert Comment

by:millardjk
ID: 38796472
When everything is up, what is the status of your spanning tree and LAG ports? Are each of the downstream connections separate? (Eg, iSW1 & iSW2 --> SW3 is one LAG, iSW1 & iSW2 --> SW4 is another)

What you describe sounds like STP is blocking traffic to iSW2 during normal operations.

When you turn off iSW2, everything is fine, because traffic from SW3-5 is all going to iSW1.

When you turn off iSW1, all traffic stops, and STP must re-converge; I suspect that if you waited 1-2min, you would find that traffic would have resumed.

The default spanning tree algorithm will set each switch at a priority of 32K, after which, the algorithm for master (and which ports are blocked) resides with the MAC address for the switch.

If you configure the iSW switches to have a higher priority (lower number = higher priority), you may find that things will work as you intend.
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by:KANEWONG
ID: 38797164
thanks!  this is what I thought something wrong on spanning tree configuration but I cannot find any hint.  I need go back to the configuration file and check.  I am using DELL PowerConnect switch.

May be I power off the iSW1 and wait for about 3 minutes to try how it work.  I tested it with about 1 minute only.
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Author Comment

by:KANEWONG
ID: 38803934
which iSW should be set higher priority? iSW1 or iSW2?
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Accepted Solution

by:
millardjk earned 1360 total points
ID: 38803939
Because the two iSCSI switches are stacked and are essentially identical in their place & role, setting the priority identically should be fine.
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