Max swap size?

Stephen Ward sjward at
Wed May 28 20:36:52 MDT 2008

Today I was poking around on a CentOS amd64 machine that keeps
randomly crashing.  I am not the sysadmin for this machine; he is on
vacation.  Anyway, I noticed something that seemed unusual to me.
This machine has 1 GB of RAM, and a grand total of 8 GB of swap
consisting of two 4 GB partitions, each on a separate drive.  These
two drives also happen to be in a RAID-1 mdadm device.

Does a 4 GB swap partition seem excessively large to anyone?  I read
the mkswap man page and found the following regarding swap

The maximum useful size of a swap area depends on the architecture and
the kernel  version.  It is roughly 2GiB on i386, PPC, m68k, ARM, 1GiB
on sparc, 512MiB on mips, 128GiB on alpha and 3TiB on sparc64.  For
kernels after 2.3.3 there is no such limitation.

The last would seem to imply that since uname tells me
"2.6.18-53.1.21.el5", there should be no swap size limitation.  Is
that correct?  Am I barking up the wrong tree here with the swap?


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