Kernel

Swap

My 48GB swap file system isn't fully recognized.

Q. FreeBSD only uses the first 32GB of a swap device.
A. Are you sure you want/need that much swap anyway? The old-school 2-4x RAM doesn't really apply, though you may want a bit more than 1x physical RAM if you are capturing a crash dump, and some systems have >32GB RAM now.

What is the best way to configure a swap backed /tmp?

Q. I want to use swap backed /tmp, but I understand it can be configured in multiple ways, including in /etc/fstab and the /etc/rc.* scripts. What is the best way to set this up?
A. Discussions here: http://forums.freebsd.org/showthread.php?t=3335, http://forums.freebsd.org/showthread.php?t=1561. Setting up from /etc/fstab: "md /tmp mfs rw,-s14336m,-oasync,-onoatime,-S,-Otime 0 0" (size, async, don't update access time, no soft updates, optimize for speed). Remember, you don't really want your system to swap, if it does, obviously, memory access slows to disk I/O speed. Via fstab:

tmpmfs="YES"                    # Set to YES to always create an mfs /tmp, NO to never
tmpsize="5g"                    # Size of mfs /tmp if created
tmpmfs_flags="-S -o async,noexec"  # Extra mdmfs options for the mfs /tmp, -S no softupdates

File Systems

Gjournaling

Are these log messages problems? "fsync: giving up on dirty" and "Cannot suspend file system"?

Q. These error messages show up frequently in messages: "fsync: giving up on dirty" and "GEOM_JOURNAL: Cannot suspend file system /xx/yy". Is this a problem? Is my journal having issues?
A. These messages are safe to ignore. http://www.mail-archive.com/[email protected]/msg196977.html Seems to be a harmless message that occurs under certain load conditions and indicates that a journal switch is pending.