vlans for performance

itdaddy

hey guys

I have a questions on vlans. Do you think vlans create better performance?

We have at our branch office huge vlans that encompass all servers
and all users at that branch? so servers and users are in same branch.

when I copy a file that is huge say 9 GB from one server to another at a loca branch, all the users at that branch are affected big time
it bogs the entire switch down, is that because the servers and users
are not in separate vlans or does that matter, ? we have a core switch 3560 poe (L3) and a 2950 vtp client at this branch.

what say you on this matter of performance. yeah it could be other things
but dont you think servers should be separate from users? or is security the only reason for vlan separation?

I thought it was collision too vlans are made?

JaCkNiFe

Considering broadcast traffic is processed by all devices within a broadcast domain, creating smaller broadcast domains (VLANs) can help reduce overhead and limit resource utilization.

cheers!

fly351

Are you using any QoS between your PC and the server? Have you verified that all interfaces are running at full duplex and 100/1000? What speed is the trunk between the L2 and L3 switches? If it is a 2950T, could you aggregate both gig ports to increase the bandwidth?

Separating the end devices into VLANs won't increase the throughput... if your transferring a 9 gig file and it is affecting the end users, then it will likely be a throughput (switch cannot process fast enough) or bandwidth issue.

GT-Rob

point-to-point transfers (unicast) will not be effected by the VLANs, it sounds with that exact problem it may be just a throughput issue (what are your links between switches?). QoS could help with this, but if a 9gb transfer is going noticed, then there are bigger issues to resolve.

I would still suggest throwing vlans on there, depending on how many users/servers you have. It makes management easier, and makes performance across the board better. ARP tables are smaller, broadcast traffic is limited, etc. At the very least, separate servers and users.

peanutnoggin

ITDaddy,

As others have already suggested, you're probably running into a limitation on the 2950. Here's the link to Cisco's Product Sheet for the 2950. This'll give you some insight on the backplane and the expected throughput (6.8Gbps) based on a 64-byte packet. HTH.

-Peanut

itdaddy

thanks guys. But this is my theory. vlans separate collision domains
so right now it is one huge collisions domain. so if I separate
the:

1. Public servers
2. internal servers
3. users

all in there own vlan, it might increase perfomance. I thought that is what cisco teaches is vlans help security which i get an performance. let collision. and i agree with the half duplex/full duplex thing. and we have GB speed between the 3560 and 2950 but on all branches remote and corp
each branch site all users and local servers to that site are all in 1 big vlan. I am not saying quantum jumps in speed I am saying with the servers in their own vlan the users would be unaffected technically due them being in separate collision domains. you know what I am saying.
and yes Qos would be good. but we have it for voice but nothing else.
we still run NetBeui so mayeb it is tooo chatti. I want to separate in vlans to separate the chatti protocols. then go from there. and sure look at speeds on ports yep. just wanted to bounce off you guys.
thanks for your input. will report back once I change it

I like users, internal servers, public servers all in their own vlans just because it is text book you know then go from there :0 but I am interested in the other aspects as well what you guys were saying. I will report back what I find. very fun stuff man way cool
and yes I am getting the IT manager job to those who thought i wasnt since I said Interim. They have to post job withing for politic reasons.
id the man! ) ahahaha thanks dudes you rock
it is late and back to my old spelling errors and grammer crap sorry mikej!
haahha;)

ptlinva

Moving the servers into thier own vlan would NOT hurt anything and it just might help with performance as well...

If the users are slow ACCESSING the servers while the 9 gigs is copying, then seperate vlans probably won't help. The issue is performance with/between the two servers.

If the users are slow ACCESSING the Internet (or doing soemthing else besides accessing the servers) while the servers are copying 9 gigs, then seperate vlans would probably help.

Good Luck! Let us know what you find out...

GT-Rob

Separates broadcast domains, not collisions


Moving users and servers to different vlans could "slow" things down because now it requires L3 routing to get over to the other subnet, however this should be minimal at worst.


How many users/servers are we talking here anyway? The reason separating broadcast domains is nice as every device on a network sends out broadcasts constantly (ARP for example), and you will limit these to the vlan. Printers should also be on their own vlan too.

I wouldn't worry about LAN QoS except for voice honestly. Unless you have extremely heavy LAN traffic, in which case you should be looking at more bandwidth (LAN bandwidth is cheap and easy). I've played with LAN QoS here but only because our server team likes to randomly run 200+gb backups during business hours through my core.



also to go back to your original question, when you say copy the 9gb file, you are talking from one server to another at the same branch right? Not crossing the WAN back to some corp/core right?

yebo2010

itdaddy wrote: »

thanks guys. But this is my theory. vlans separate collision domains
so right now it is one huge collisions domain.

Nope. Its one broadcast domain AND NOT a COLLISION domain(unless you are using half duplex settings).

As others have already said, VLANs were created to separete broadcast domains rather than increase throughput. The only reason you could suspect VLAN being the culprit is when you have clients sending alot of broadcasts(e.g if your transfer operation required broadcast packets to be sent). Since the transmission media is the same no more bandwidth is created by using more VLANs(since its the same switch, same cable and same router perhaps)

Instead of focusing on creating more VLANs, perhaps you could focus more on creating etherchanels to aggregate bandwith and implementing QoS techniques. Study the traffic pattern and see where is the bottleneck.

My 2 cents

rwwest7

There's a great program called Qcheck, you should check it out. In any switched network transfering a large file from one PC to another should not bring down everyone else. That sounds more like the old 10 meg hub days. That Qcheck program will tell you if you have a choke point between two PC's.

itdaddy

ptlinva said:

If the users are slow ACCESSING the Internet (or doing soemthing else besides accessing the servers) while the servers are copying 9 gigs, then seperate vlans would probably help.

yeah this is one of them. I was just think everyone is in one huge collision domain. and yeah going to check for bottlenecking. agreed.

you bet I will let you know. It may takes some time since I have
wait for contracts to expire to get my hands dirty hahaha
but I am chomping at the Cisco bit.

wow what a great response..

I do see what you mean it really could be a lot of things but that was one of my pet peeves was each branch was in 1 huge vlan. I just want

users in vlan
public servers in their own vlan
internal/local to branch in their own vlan
and of course we have our voice servers in their own vlan already

something like this to follow a good sound perfromance model

but I will for sure report back give me some time and I will report back
nothing better than live stufff )

itdaddy

rwwest7

choke point yeah I was thinking of that too it is going to be fun figuring this out. but once our contracts expire it is do it right time
hee hee
or at least learn to do it right time

itdaddy

yebo2010

ahhhhhaah oops man need to refresh. I was thinking of what you are saying but I mixed up the two words ahhha omg do I need to refresh
you are right broadcast domains is right.
thanks for reminding me. getting old..

mikej412

itdaddy wrote: »

getting old..

I just though you were moving up the food chain at work into management

itdaddy

hhahahaha you know mikej you get old and think one thing but say another.
what is really cool is my new boss the president is going to let me get more training and pay for my certs (wow) and so I can stop saying dumb stuff like
collisions when I really mean broadcasts...ahhaa and i think they might
pay for some better english classes ahahahah

yep it should be official in 2 weeks so pumped

mikej412

itdaddy wrote: »

it should be official in 2 weeks

At which point we will be expecting proper (or at least better) capitalization, punctuation, spelling, and grammar in your posts.

I hope that doesn't add to much pressure along with the new job responsibilities.

sides14

Definitely segment traffic by department (you don't want everyone on the same VLAN that your servers are located on). If you are regularly moving that much traffic, ditch the 2950 and go with something a little more power. Implement QoS so your work does not interfere with the regular business operations.