How to limit the size of the moon?

Question

iSCSI

Hello.
I'm making a diskless system for an internet club.
Disks are created by such a script, then distributed via iscsi:

modprobe dm_mod
modprobe dm_mirror
modprobe dm_snapshot
 
IMAGE_FILE=$1

DIRCLONE=/storage3/clon
 
img_loop_dev=`losetup -f`
 
losetup -v -f $IMAGE_FILE
 
cow_size=`blockdev --getsize $img_loop_dev`
echo $cow_size
chunk_size=64
# chunk_size=1
 
FILE=$IMAGE_FILE
 
for loopnumber in 0  1  2  3  4  5  6  7  8  9  10  11  12  13  14  15  16  17  18  19  20  21  22  23  24  25  26  27  28  29  30  
do
dd if=/dev/zero of=$DIRCLONE/$FILE.cow.$loopnumber bs=512 count=0 seek=$cow_size
COWLOOPDEV=`losetup -f`
losetup -v -f $DIRCLONE/$FILE.cow.$loopnumber
echo "0 $cow_size snapshot $img_loop_dev $COWLOOPDEV p $chunk_size" | dmsetup create $FILE.cow.$loopnumber

done

Question:
how to limit the client the amount of writing to your disk?