I am configuring a new network and had a couple questions I am finding hard to find good answers about best practices on using VLANs to separate Core network traffic and iSCSI traffic.
The switches for the core network are a Cisco 24 port 3560X doing layer 3 VLAN routing and three 3560x 48port. I have 3-4 servers that on the SAN with average of 7-10 VM's per host. Am I overloading the switches with that amount of traffic ? Am I better off doing completely dedicated switches for the SAN?
Best Answer
Yes you are asking for trouble. In order to get good performance out of iSCSI, you need to enable jumbo packets on the switch. On the 3560, you're only able to set MTU size for the entire switch, not individual ports. So you'd have to set a higher MTU for the entire network which may lead to more problems that you'll have to deal with.
In addition to that problem, you're adding more complexity to a very critical portion of your infrastructure. In addition to that, you're introducing potential security vulnerabilities as VLAN hopping can be a real concern when everything is not setup correctly.
You also have to worry about performance on the switch. iSCSI is very sensitive to performance issues. You may be overloading the switch by having it do both your network and SAN.
Stay away from it! Buy a dedicated switch for your iSCSI network and you'll have no regrets.