XFS和RAID6性能优化

#!/bin/bash
#author by John Sun
#=======================================================================================================================+
#What is the significance of the file system block size?                                                                |
#If my fs block size is set at say 8K does that mean that all read/write I/O will happen at size 8K?                    |
#So if my application wants to read say 16 bytes at offset 4097 then a 4K block starting from offset 4096 will be read? |
BLOCKSIZE=4096 # Make sure this is in bytes                                                                             |
#=======================================================================================================================+

#=======================================================================================================================+
#if you want big I/O requests, you should opt for smaller RAID chunk sizes, and if I/O will be small,                   |       
#you should go for larger chunks.                                                                                       |
CHUNKSIZE=256  # Make sure this is in KiB                                                                               |
#=======================================================================================================================+
NUMSPINDLES=24
RAID_TYPE=6   
RAID_DEVICE_NAME="/dev/md-2" # Specify device name for your RAID device
#FSLABEL="source" # specify filesystem label for generating mkfs line here

case "$RAID_TYPE" in
0)
    RAID_DISKS=${NUMSPINDLES};
    ;;
1)
    RAID_DISKS=${NUMSPINDLES};
    ;;
10)
    RAID_DISKS=${NUMSPINDLES};
    ;;
5)
    RAID_DISKS=`echo "${NUMSPINDLES} - 1" | bc`;
    ;;
6)
    RAID_DISKS=`echo "${NUMSPINDLES} - 3" | bc`;
    ;;
*)
    echo "Please specify RAID_TYPE as one of: 0, 1, 10, 5, or 6."
    exit
    ;;
esac

SUNIT=`echo "${CHUNKSIZE} * 1024 / 512" | bc`
SWIDTH=`echo "$RAID_DISKS * ${SUNIT}" | bc`

echo "System blocksize=${BLOCKSIZE}"
echo "Chunk Size=${CHUNKSIZE} KiB"
echo "NumSpindles=${NUMSPINDLES}"
echo "RAID Type=${RAID_TYPE}"
echo "RAID Disks (usable for data)=${RAID_DISKS}"
echo "Calculated values:"
echo "Stripe Unit=${SUNIT}"
echo -e "Stripe Width=${SWIDTH}\n"
echo "mkfs line:"
echo -e "mkfs.xfs -b size=${BLOCKSIZE} -d sunit=${SUNIT},swidth=${SWIDTH} ${RAID_DEVICE_NAME}\n"
echo "mount line:"
echo -e "mount -o remount,sunit=${SUNIT},swidth=${SWIDTH}\n"
echo "Add these options to your /etc/fstab to make permanent:"
echo "sunit=${SUNIT},swidth=${SWIDTH}"