2G Swap File Limitations

[rmlfcu]

Can anyone help me out? Traditionally, in the past when building a Fedora Core OS, I have always created multiple 2G swap files as opposed to 1 big swap file because I have read that Linux has a 2G swap file limitation. I am in the planning stages of building a Dell R900 with 1.5TB of available space, Raid 5. This box will be running a Fedora Core 9 - 64bit OS with 64G of RAM. Can anyone tell me based on this information if I am still dealing with swap file limitation sizes of 2G or does this limitation no longer exist with this type of platform. Assuming there is no longer a limitation on swap file sizing, am I free to create 1 swap file the size of my choosing up to 64G without any performance issues? Or if the 1 big swap file would cause performance issues, would I be better off creating 3 or 4 swap files each with a size of 16G?
I would greatly appreciate anyone's help on this one.
Thanks, Rob

[vitalka]

I take it that this machine will be a server. In that case if you're ran out of ram then consider adding more ram. HD will slow down your server especially if you have a full 16GB SWAP.

And maybe it's just me but I never heard of SWAP limit. For a desktop PC rule of thumb is: SWAP is twice as big as the amount of ram, though that doesn't apply any more since ram is not an issue this days.

[HROAdmin26]

The mkswap utility *used* to have a 2GB limit - YEARS ago.

Forum Thread

I can't see even a 16GB swap being useful. Do you expect to burn thru 64GB RAM and *need* swap? You may want to review *why* you have a swap file.

Depending on what you're running and how you're utilizing RAM, I'd either have *no swap* or something like 2-4GB.

You can also look at a kernel tuning parameter called "swappiness."

[bigtomrodney]

I wouldn't bother with Swap at all to be honest. If 64GB isn't enough I'd suggest that swap won't help. If your system has 64GB to play with without the addition of swap it would (from my experience) manage better. Remember using swap would add to disk i/o and if it's a fileserver that would be more important than RAM.

[Bikerepairmann]

I too have heard about the 2GB max. With a 64GB RAM in your system, I wouldn't bother with more than 1GB. If it needs to access the swap with that amount of RAM, I think there are other problems. Some optimisation would be my first thought

[ne1scott]

I am in a very similar situation. I guess the only reason I am considering creating a swap file at all is because it always said to have one wherever I read, so I never even considered "Not" having a swap file. I assume a kernel dump might use it, but other than that maybe it is truly a waste of time creating one when you have 64GB of RAM in the system. If you've burned through the first 64GB, then a 2-4GB swap file isn't going to last you long and will give you a performance hit when using it.
You can follow the questions I asked in my thread post at http://www.linuxforums.org/forum/red...tml#post612682