I'm a newly register user, i've been reading the forum here and there. I've got a Rpi with 24 usb erupters running raspbian. The interesting part is with running that many erupters on the RPi is loads would got as high as 7.50 which slow the system. However, it still submitted shares just fine and slush is reporting normal ~8GH. What I found is there is a need to remove any usb bluetooth, usb wifi dongles have significantly reduce load avg from 7.5 to 4.8. a big reduction. My setup require latest raspbian with latest hexxeh's rpi-update firmware with cmdline.txt with arguments "dwc_otg.speed=1 smsc95xx.turbo_mode=N " added and modified sysctl.conf line with vm.min_free_kbytes to 16384. Running cgminer 3.4.2. so far it has been running for 80 hours.
Welcome and interesting setup. I dont have so many usb erupters though
with latest standard raspbian you can have up to 11 usb erupters on one usb port, given using a usb hub that can power all the erupters with each one taking max of .51A (for variance), without any special changes i mentioned above.
Well, i figure if i dont have to keep my desktop on all the time, the savings in electricity each month would be enough to buy an erupter, I used kill a watt and found that my average cost per month for keeping the computer on was around ~28 bucks. However i could buy a laptop but no point since i already have the pi. Also, its more cost effective to use the pi in terms of power.