There's a small bug in SCSI drive hotplug where QEMU is not assigning
unique block device names when you leave the name unspecified
$ /home/berrange/usr/qemu-0.12/bin/qemu -vnc :1 -monitor stdio -device lsi
QEMU 0.11.91 monitor - type 'help' for more information
(qemu) drive_add 0:0:4 file=/home/berrange/mcdboot.img,if=scsi
OK bus 0, unit 0
(qemu) drive_add 0:0:4 file=/home/berrange/mcdboot.img,if=scsi
OK bus 0, unit 1
(qemu) drive_add 0:0:4 file=/home/berrange/mcdboot.img,if=scsi
OK bus 0, unit 2
(qemu) drive_add 0:0:4 file=/home/berrange/mcdboot.img,if=scsi
OK bus 0, unit 3
(qemu) info block
ide1-cd0: type=cdrom removable=1 locked=0 [not inserted]
floppy0: type=floppy removable=1 locked=0 [not inserted]
sd0: type=floppy removable=1 locked=0 [not inserted]
scsi0-hd0: type=hd removable=0 file=/home/berrange/mcdboot.img ro=1 drv=raw
encrypted=0
scsi0-hd0: type=hd removable=0 file=/home/berrange/mcdboot.img ro=1 drv=raw
encrypted=0
scsi0-hd0: type=hd removable=0 file=/home/berrange/mcdboot.img ro=1 drv=raw
encrypted=0
scsi0-hd0: type=hd removable=0 file=/home/berrange/mcdboot.img ro=1 drv=raw
encrypted=0
(qemu)
Notice they are all 'scsi0-hd0', instead of scsi0-hd1, scsi0-hd2, etc