My 8 drive RAID array is a little weird. Throughput is decent, but latency is kinda bad. This causes World of Warcraft for mac to not be able to keep up when recording in-game video at high data rates (200+ MB/s), which of course is the only way to get large frame size *and* high frame rate :) It took me literally years to finally think of this …

wow_ramdisk.sh

#!/bin/bash
set -x

# 11/3/2013 - dre at mac dot com

# Create a ramdisk big enough for World of Warcraft (mac version only!) to
# store a few video capture files. Shortly after each file is written, copy it
# to rotational storage, delete it from the ramdisk, and then symlink it from
# rotational back to the ramdisk.

# This might sound like a silly thing to do, but this little dance works around
# a real problem. Because WoW's video capture file segment size is fixed, as
# capture rates get higher, more filesystem work is required. Eventually, the
# overhead of managing the files (creating / stating) becomes too much for my 
# prosumer grade storage array, and it chokes, even though it has more than
# enough throughput to lay the bytes down in time. It's the latency of the file
# operations that seems to be the problem.

# My workflow goes like this:
# - Start the script; it creates a ramdisk and begins monitoring it
# - Fire up WoW, make sure it's set to store video files on the ramdisk.
# - Do some recording

# At this point, I do one of two things:
# 1) If the finished (compressed) video would fit on the ramdisk, it's safe to
#    compress immediately.
# 2) If it wouldn't fit, or if there are many captures, rename the sub-dir in
#    the ramdisk, then symlink the rotational storage directory to the same
#    path that was used on the ramdisk when capturing. Now the raw files can be
#    compressed like normal.

# Size of ramdisk to create (megabytes * 2048)
SIZE=16777216   # 8 GB
RAM="/Volumes/ramdisk"
DIR="wowmovies"
DEST="/Volumes/collider/wowmovies/slurp"

function checkFail {
    if [ $? -eq 1 ]; then echo "Failed: ${OP}" && exit 1 ; fi
}

# If there's nothing at our ramdisk mount path, let's make something
if [ ! -d ${RAM} ]
then
    # Name of new volume to host the ramdisk
    VOLNAME=$(basename ${RAM})

    OP="Make a ramdisk device."
    DEV=$(hdiutil attach -nomount ram://${SIZE} | cut -d' ' -f1)
    checkFail

    OP="Install a filesystem on our ramdisk..."
    diskutil erasevolume HFS+ ${VOLNAME} ${DEV}
    checkFail

    # Wait for notifications to ripple out before turning off spotlight
    sleep 2

    OP="Disable spotlight on our ramdisk."
    mdutil -d ${RAM}
    checkFail
fi

# Double check that our ramdisk is there before proceeding
if diskutil info ${RAM}
then
    echo "ramdisk located... proceeding."
else
    echo "ramdisk unavailable!"
    exit 1
fi

cd ${RAM}
mkdir -p ${DIR}
cd ${DIR}

# Loop forever, monitoring the ramdisk, and moving the new files.
while true
do
    find -s . \
        \( -name "*wvd*" -or -name "*wav" -or -name "*wvd" \) \
        -type f \
        -mtime +3s | while read f
    do
        #nice -n 20 cp -p ${f} ${DEST}
        nice -n 20 mv ${f} ${DEST}
        ln -s ${DEST}/${f}
    done
    sleep 1 
done