To Switch or to Pass Through Module


We are planning to change from IBM servers to Dell Power edge M620 blade servers. right now our SAN storage EMC VNX 5300 with 2 brocade DS-5100B switches. 

now how the M620 blade servers will connect to our existing EMC SAN storage???Dell people they suggest 2 brocade M5424 FC8 switches. but i don't understand how this configuration will be done since i already have 2 brocade switches???? 

after searching on dell website i found Pass Through module and i understand that it will only pass the fiber connection to the existing brocade switches. so no need for the 2 brocade switches which dell propose.

 Can you help me in this and share with me your idea about this issue. shall i go to switches or get Pass Through module.

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2 Replies

RE: To Switch or to Pass Through Module

With blade FC switches you can use access gateway features (active by default) that permit easly to threat them as pass-thought switches.

Just 2 cables per switch that are similar to a LAG in Ethernet switches

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RE: To Switch or to Pass Through Module


There are many advantages of using PTM(Pass through) as you have an existing FC SAN infrastructure. Prime advantages are listed below.

  1. Unlike a switch or access gateway, there is no need to configure anything like zoning or link speed or flow control – there is none of that, the PTM simply Passes The Signal Through (no mgmt. interface)
  2. FC PTMs are completely interoperable with any SAN Fabric without issue, whether based on Brocade or Cisco switches,
  3. Since the PTM is a non-blocking solution there is no chance for the traffic to be slowed down. Non-blocking means there is no firmware or hardware in the I/O path deciding which I/O to forward to the destination, because each path is dedicated. There are several performance benefits to consider when deciding whether to use a PTM or a switch, such as:
  • An FC PTM port provides a per port dedicated non-shared bandwidth between each server and SAN Fabric
  • An FC PTM port provides fully isolated I/O for each connection
  • An FC PTM port provides 2X greater total I/O bandwidth than Fabric Switch Blades
  • An FC PTM port provides a non-blocking solution whereas fabric switches & Access Gateways can have up to 50% blocking with more than 8 servers


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