Recommended Gigabit Switch/Module

Answered Question
Apr 7th, 2010

Hi,


We are looking for a real 1Gbps per port switch.
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John

I have this problem too.
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Correct Answer by Jon Marshall about 6 years 8 months ago

johnpatricklopez wrote:

I think they are planning to connect a dedicated NIC of the backup server to the separate switch and other servers' NICs as well. So the backup will just be local to the switch. They found out that their servers can run up to 800Mbps during backup when they tried to connect the servers back to back using cross cable I think. So that's the reason why they asked us why they are only getting 200Mbps on a 6500 switch and luckily I found the reason why and it's because of the 8:1 oversubsription. They need to backup almost 4TB of data every week.

John

Well the 4948 is designed for server connectivity with low latency throughput. The 3750-E/X series switches are also non blocking so you could also consider these but with these they are primarily designed for wiring closets eg. providing PoE which is obviously not needed for your requirement.

If you can i would get both on loan and do some testing although i would lean towards the 4948 switch based on what you need.

Jon

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Jon Marshall Wed, 04/07/2010 - 03:36

johnpatricklopez wrote:

Hi,


We are looking for a real 1Gbps per port switch.
We recently found out that WS-X6548-GE-TX and WS-X6148-GE-TX modules for Catalyst 6500 cannot provide 1Gbps per interface. The 1Gbps ASIC is being divided into 8 ports instead. What are our options? Thanks guys.


John

John

If you have a supervisor 720 then you should go for the WS-X6748-GE-TX. This is a 48 port 10/100/1000 module. It has a 40Gbps connection to the switch fabric so there is a small amount of oversubscription ie. 48 x 1Gbps dived by 40Gbps to switch fabric but it is very unlikely you will be running all 48 ports at 1Gbps throughput simultaneously.

Jon

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John Patrick Lopez Wed, 04/07/2010 - 03:42

Thanks for the reply. We are not running Sup720 and we are just using Sup2.  What about standalone switches? I am looking at the data sheet of Catalyst 4948 and I don't know if this can provide pure 1Gbps per interface. It says that it has a 92Gbps non-blocking switch fabric and I'm not sure what it means. Are there any lower models that can run 1Gbps per interface?

Jon Marshall Wed, 04/07/2010 - 03:50

johnpatricklopez wrote:

Thanks for the reply. We are not running Sup720 and we are just using Sup2.  What about standalone switches? I am looking at the data sheet of Catalyst 4948 and I don't know if this can provide pure 1Gbps per interface. It says that it has a 92Gbps non-blocking switch fabric and I'm not sure what it means. Are there any lower models that can run 1Gbps per interface?

John

Okay with a sup2 you are not going to get a 10/100/1000 module that does what you want even if you were running an SFM (Switch Fabric Module).

The 4948 is a non-blocking wirespeed architecture. Simply put this means you can indeed run all ports at 1Gbps simultaneously without any blocking. Obviously that is local to the switch. If you have to uplink the switch to another switch then be aware of the oversubscription issues on the uplinks.

Jon

John Patrick Lopez Wed, 04/07/2010 - 03:56

Thanks. Do I have other options? Our server team is quite concern about the speed of their backup servers over the network. They are complaining that they aren't getting more than 200Mbps on a gigabit interface so we are looking for other options where we can transfer their servers and provide the speed that they need. So yeah, the 4948 is an option right? What else? I am looking at some data sheets but I don't trust the data Cisco has given. I mean there are things that is not on writing.

Jon Marshall Wed, 04/07/2010 - 04:13

John

The backups, are they having to go across uplinks between switches and what speed are these uplinks ?

Bear in mind also that a lot of applications struggle to fully utilise available bandwidth so it may not be a network issue at all. On your existing modules are you seeing lots of drops ?

Ideally with backups you want the backup server connected to the local switch if you have a lot of traffic to backup. Do you have dedicated NICs on the servers for backups ?

The 4948 is designed for server farm connectivity. Other switches like the 3750-Es etc. are also near wirespeed performance but then you have to start looking to buffers etc.

Trouble is there are so many variables that can affect server performance. You say your server guys are only getting 200Mbps per server at the moment, is the backup server connected to the same switch. If you purchased a 4948 then yes you would get wirespeed on that switch but then if the backup server remains on the 6500 you now have serious oversubscription on the uplinks from the 4948.

So a few more details would help.

Jon

John Patrick Lopez Wed, 04/07/2010 - 04:35

I think they are planning to connect a dedicated NIC of the backup server to the separate switch and other servers' NICs as well. So the backup will just be local to the switch. They found out that their servers can run up to 800Mbps during backup when they tried to connect the servers back to back using cross cable I think. So that's the reason why they asked us why they are only getting 200Mbps on a 6500 switch and luckily I found the reason why and it's because of the 8:1 oversubsription. They need to backup almost 4TB of data every week.

Correct Answer
Jon Marshall Wed, 04/07/2010 - 04:58

johnpatricklopez wrote:

I think they are planning to connect a dedicated NIC of the backup server to the separate switch and other servers' NICs as well. So the backup will just be local to the switch. They found out that their servers can run up to 800Mbps during backup when they tried to connect the servers back to back using cross cable I think. So that's the reason why they asked us why they are only getting 200Mbps on a 6500 switch and luckily I found the reason why and it's because of the 8:1 oversubsription. They need to backup almost 4TB of data every week.

John

Well the 4948 is designed for server connectivity with low latency throughput. The 3750-E/X series switches are also non blocking so you could also consider these but with these they are primarily designed for wiring closets eg. providing PoE which is obviously not needed for your requirement.

If you can i would get both on loan and do some testing although i would lean towards the 4948 switch based on what you need.

Jon

John Patrick Lopez Wed, 04/07/2010 - 05:31

Thanks for the suggestion sir. I am guessing that what if, we put the backup server into port 1 of a 3750 then put nothing on port 7 to 8. Then the servers will be connected to port 9 to 24. Do you think I will get a full 1Gbps since the traffic will be switching using different ASIC. This article is also helpful.

http://puck.nether.net/pipermail/cisco-nsp/2006-September/034721.html

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