I have a SRX 650 and it is booting up to it's backup image.
When I run the command "request system snapshot partition slice alternate" I recieve the following output.
root@Kona> request system snapshot partition slice alternate Formatting alternate root (/dev/ad0s1a)... Copying '/dev/ad0s2a' to '/dev/ad0s1a' .. (this may take a few minutes) error: /dev/ad0s2a copy failed
When I run the command "show system snapshot media internal slice 1" to look at the snapshots it does not show the primary partition.
root@Kona> show system snapshot media internal slice 1 Information for snapshot on internal (/dev/ad0s2a) (backup) Creation date: Jun 1 00:14:19 2012 JUNOS version on snapshot: junos : 11.4R3.7-domestic
Also when I run the command ls /dev this is what I see.