On 2015-02-15, Gregory P. Ennis PoMec@PoMec.Net wrote:
I am putting together a new mail server for our firm using a SuperMicro with Centos 7.0. When performed the install of the os, I put 16 gigs of memory in the wrong slots on the mother board which caused the SuperMicro to recognize 8 gigs instead of 16 gigs. When I installed Centos 7.0, this error made the swap file 8070 megs instead of what I would have expected to be a over 16000 megs.
You lucked out, honestly. You really don't want 8GB of swap on your system. What will most likely happen is that you'll have a process that starts running away eating memory, and it'll try to use all of that swap before the kernel's OOM killer can kick in. You will not enjoy thrashing 8GB of swap for probably hours.
Really what you should do is drastically reduce the amount of swap you have allocated, and reclaim most of that 8GB of swap space for storage filesystems. In my experience, a few hundred MB of swap is more than sufficient to be able to swap out seldom-used memory while not taking too long to OOM. If you really find a need for more swap later, you can allocate a swap file; it's slightly less efficient than a swap partition, but compared to real memory the difference will be negligible.
--keith