Quote from Timo on August 31, 2011, 14:35
I think having some extra swap space (or place for /tmp) not on the SD is nice to have. But as mentioned earlier flash-sticks have a limited number of writes. So I searched around for an USB device with volatile memory (DRAM or similar), but I just found a SATA version, which get close: http://techreport.com/articles.x/16255
Further search only delivered a bunch of posts about whether there is a use case for that or not.
Most flash based devices have wear levelling these days. It's cheap enough to produce on the varying on-board controllers for the devices that you're going to have something REALLY old or really, really cheap (read: Do not use...ever...) these days.
Since that's the case, you're going to go 3-ish to 5-ish before it might become a bit of a problem with SD's or with any USB thumb you can purchase these days that's not a dodgy thing to use.
Having said this...if you could find someone that could make a 512-2048MB SRAM based and battery/supercap backed thumb and have it be priced reasonably...heh...it'd make for a super thumb and swap space.
Such a device could be delivered as an extension module for the r-pi. How much bandwidth do the gpio (or other connectors) give? Connecting through these extra pins would avoid sharing bandwidth with ethernet and usb devices.
It could be realized as a simple version of a SoC with PoP-RAM as the r-pi itself has. Hence the extra costs of 10$ for model B splits to 128MiB RAM and the LAN chip, 128MiB on a very simple SoC shouldn't cost that much (given there is a SoC which simply forwards the RAM as a Ramdrive).
Theoretically, there's enough bandwidth out the GPIO's to drive 1Gbit Ethernet rates, if you can push the peak signalling rate. Problem is, there's no hardware to help you do this there and the CPU'd just be pinned dealing with the data if it COULD manage the data rate. Not likely to be a pathway for things there.