In response to your original question, I have unRaid installed on a 2GB Sandisk.
Around Thanksgiving I found a 2GB Sandisk Cruzer Micro for $13, so even though it is overkill for this, I bought it. I did have some issues trying to get it to run unRaid. The issue was the "U3" capabilities of the drive. Sandisk adds software and maybe a partition so that when you plug it into a Windows machine, it comes up as two drives--a CD-ROM and a flash drive. You cannot delete files off the CD-ROM part and when I tried to copy the unRaid files to the USB part, it would not boot in the unRaid