Help with Oversize packets

Hi guys, just looking to see if i am on the right track here.

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I have 16 blade servers running a 1GB network on some Dell PCM6348's

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Before Wednesday night, all my servers had no VLAN tagging. On the switches i configured each port manually to tag them on VLAN 100 as this was the only VLAN we used.

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On Wednesday i configured more VLANs for blades 12-16, these were set on the server so i have a Virtual Switch with a VLAN of 100 and another Virtual Switch with a VLAN of 106. I didn't see any issues and things seemed to work.

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Queue Thursday morning, i come in to work and all hell is breaking loose. We have 2 applications that are crashing left and right and users are complaining its taking ages to save files to the network compared to normal.

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I moved all the data to different blades i hadn't changed and it all started to work normally again now. Looking in to it, under the port statistics for blades 12-16 i am getting millions of "Oversize Packets". Upon further reading i believe this is because the MTU is set to the default of 1518 and the VLAN tag adds 4 bytes making it 1522 which is too large.

Does this sound right? Do i need to just globally up my MTU packets to 1522 and then change it at the port level also?

Maybe i'm on the completely wrong path, however any help would be greatly appreciated! I am not really a network guy as we only have a couple of switches.