Question about multiple network cards

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Question about multiple network cards

Postby gutt3d » Sat Jun 28, 2008 3:26 am

I have an ongoing problem whereby on occassion one of my fileservers simply stops responding - it's like the TCP stack has locked up. It runs headless but on the rare times it's locked up while it's been hooked up to a monitor and keyboard then it's clear that the system is working fine, but just that I can't connect to it via the ethernet port. As I say - it's an ongoing problem that I've been suffering with this fileserver since day one - it's most likely because there is a BT client running on it.

But anyway - that's not the reason for my post here. Assuming that I'm actually correct in that the TCP stack has locked up for some reason, then here's my question...

If I install another NIC, do you reckon it will be possible to connect on the "backup" NIC if the primary one goes down? Like - if the TCP stack really is frozen, will it only affect one NIC or will it affect all NICs?

I've recently got a new motherboard for that fileserver with a built-in gigEthernet port. I'm thinking about installing the current gigEthernet NIC into the replacement motherboard and have 2 NICs to make the fileserver multi-homed.

I know that I need to address the fact that it locks up - honestly, I really do know this. I've tried various different BT clients, various different settings, and have been battling with this on and off for well over 2 years. My post here is not about fixing the lock-up - it's more about finding workaround or a way to recover (perhaps by accessing via another NIC to reboot) when the problem comes back (which it inevitably will). It just saves me having to go out into the "server room" late at night - the problem happens randomly, but it's most annoying when my wife and I are watching TV shows directly from the server at night and I have to manually go outside to reboot the server. Even more annoying when it's raining. But I digress...

Multi-homed fileserver. Yay or nay?
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Postby Chozo » Sat Jun 28, 2008 6:46 am

If you are correct and TCP/IP is locking up, adding a second NIC would not help you work around your issue. Before I moved to the server support team, I used to get laptops where neither the wired nor the wireless NICs worked and repairing the TCP/IP stack (or reloading the OS) fixed it.

However, I do not think that adding a second NIC is a bad idea, especially since this is a file server. If you can use NIC teaming (or bonding, link aggregation, whatever you want to call it), you do get the benefit of fault tolerance and also some load balancing. At the very least, it would give you another NIC to test.
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Postby gutt3d » Sat Jun 28, 2008 7:39 am

Cool - thanks for the advice.

My guess, FWIW, is that the number of open and/or half open sockets is preventing further connections being made (hence why I can't ping the fileserver when it locks up). I suspect that the stack is becoming overloaded with all these connection or (connection attempts) because of the BT client.

When the problem happens, I don't need to reload the OS or repair the stack - all I need do is reboot the machine and all is good for a while.

Interesting idea about NIC teaming: I'd not thought about that :) Good call! In fact - now you mention it, I'm wondering whether it's worth installing another NIC into my other fileserver so I can benefit from teaming :)

Anyway - thanks again dude.
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