Solved: Cisco MDS speed

rmohanraj · ‎03-01-2007

I am looking to have information about port to port latency on cisco

1- Port to Port latency of port on same port group and cross bar

2 - What is the subcription ratio.

Basically I am in process of selecting between Brocade 4800 vs MDS.

skurganov · ‎03-01-2007

Check out performance testing by Miercom, it has latency range/distribution based on frame size.

http://www.cisco.com/application/pdf/en/us/guest/products/ps4358/c1244/cdccont_0900aecd800cbd65.pdf

"The MDS 9509 showed excellent performance regardless of frame size. It achieved near line

rate with small frames (98.67%) and full line rate with large frames, both with 100% intended

load. Regardless of the load, the minimum latency for both frame sizes was very consistent. For

small frames, it varied from 7.2 to 52.9 ?s under 100% intended load. For large frames, the

latency ranged from 19.7 to 218.9 ?s under 100% intended load. Furthermore, the MDS 9509

was able to sustain traffic at a much higher throughput rate for minimum- and maximum-sized frames while maintaining a more consistent latency then other switches tested."

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mfrase · ‎03-01-2007

There are other Cisco whitepapers on switch architecture at,

http://www.cisco.com/en/US/netsol/ns512/networking_solutions_package.html

One on more detail of the LC's and crossbars at,

http://www.cisco.com/en/US/netsol/ns512/networking_solutions_white_paper0900aecd8044c7e3.shtml

Any of the resellers, pick one, has access to Cisco Technical Marketing to address your questions directly with regards to Brocade vs Cisco

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mfrase · ‎03-01-2007

You need to be careful here when comparing latency numbers between vendors, it is never apples to apples because of frame size used in measurement. The Cisco reseller you would be getting switch from will help you evaluate the numbers correctly. As for port to port or crossbar in the MDS there is no difference. As for subscription ratios you can read about the Line cards at http://www.cisco.com/en/US/products/ps5991/products_data_sheet0900aecd80446058.html

The 16 port LC has no over subscription, the 24 & 48 are user configurable in many different bandwidth choices. see link for greater detail:

http://www.cisco.com/en/US/products/ps5991/products_white_paper0900aecd8044c807.shtml

rmohanraj · ‎03-01-2007

I understand , it is never apple to apple comparision.

These links provide very generic standard information about switch. But not discussing about speed/latency between port set and cross bar. I am looking for these specifc information.

Do you happen to know any reseller whom I can contact for these information.

stephen2615 · ‎03-01-2007

I have been in the process of looking at the different switches and I assume you mean the Brocade 48000 not a 4800. You also did not mention which MDS you were looking at.

The 48000 has some interesting facts that are not all that well advertised especially if you are looking at large port numbers on the 48000. Overall, the Brocade "appears" to have more backplane speed but to be honest, there are not many systems that could use that speed.

The 32 and 48 port cards are oversubscribed at 2 - 1 and 3 - 1 respectively. That still appears to be better than the 48 port cards offered by Cisco but thats a personal choice.

The other major thing to worry about is redundancy of the CP's for the 48000. They are not really fault tolerant if you want to keep all your ports operational. Brocade talks about 34 years MTBF hoping that you wont lose a CP.

Have a look at:

http://www.brocade.com/san/pdf/whitepapers/Achieving_Ent_SAN_Perf_48000_Dir_WP_01.pdf

I dont wear rose coloured glasses when it comes to speed and/or performance figures. Sheer grunt does not mean blistering figures made up by some paid consultant.

I want the ability of the product to fill my needs and to get decent support. So far Brocade fails miserably on both accounts.

Stephen

rmohanraj · ‎03-01-2007

Stephen,

Thanks for your clarification

I read this document couple of times, CP is fault tolerent. on CP failure all ports will operate normally ( backplane power would be half either with cisco or brocade ). The document has some intersting numbers about latency and cross bar speed. I am looking for similar official numbers if available from cisco.

Mohan

stephen2615 · ‎03-01-2007

Hi Mohan,

I have never fully believed the CP failure story from Brocade with over subscribed ports and I have no intention of trying it on our production systems...

I do believe that you can lose a MDS supervisor card without any performance loss or at least thats what my Cisco tech says. The 9513 is different to the 9506 and 9509 in some way with using the supervisor cards but I am not clear on that.

Brocades port group cross connect without going through the back plane seems pretty good until you consider what you would be using them for. Why would you consider putting heavy usage devices in an over subscribed port group?

I think the Brocade (McData) Mi10K Director is a much better piece of kit than the 48000 which is basically a BIG (almost dumb) quick switch that is not in the same league as the MDS. Our investment in the 24000's shows that we can't do anything other than switch which is a problem as the other datacenter has 48000's.

Brocade also claim to have fixed the master ISL issue and supposedly the 48000 also does not have any head of line blocking problems. QoS does not match VSAN QoS in a fit. So when I do backups in the fabric to the other datacenter in a paired DR solution, I have hoped to not affect our synchronous true copy. This bothers me as if one of the drives has problems, this could reduce the throughput to the other datacenter's drive and head of line blocking had better not be an issue.

I would prefer to be able to do VSAN and IVR any day of the week and SAN Extension with the MDS is more comfortable to me.

One thing that really peeves me is that there is no Brocade Forum so asking simple questions about usability is almost impossible.

I want to do ISL trunking but I need a special licence for that.

I am not keen on the troubleshooting capabilities of the Brocade switches.

To be honest, I don't see any difference between Qlogic and Brocade switches other than Qlogic works in native interop mode.

Anyway, enough of my observations.

Cheers