how to make the live-usb boot faster ?

[born]

hi all.
I make a custom live cd by using remastersys.
after that,I use the USB-creator install the ISO on my USB key. it could
bootup into the desktop. in this way,it use about 90 scends to bootup.the
live-usb key could save data.

then I use the unetbootin to make the live-usb.At this time,it use 63 scends
to bootup,but can't save data.
I have search it,find a web page about how to make it persistent.
the web page's link is
http://unetbootin.sourceforge.net/diskimg/readme.txt

I follow the setups try to make it persistent,and failed.

when the live-usb bootup,there is an error use about 20 scends.
"init: line 1 : can't open /dev/sr0 : no medium found"

my goal is to make a live-usb,which bootup fast and could save data.

are there someone coule help me?
thanks anyway.
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