On Thu, 2008-12-18 at 09:13 -1000, Mitch Bradley wrote: > John Gilmore wrote: > > Swapping to the soldered-in NAND chips is a very bad idea. It will > > tend to wear them out rapidly. Even if you use load-leveling software > > (e.g. swapping to a file in a jfffs2 filesystem), the problem is that > > if you do start wearing out serious numbers of flash blocks, the > > laptop becomes toast; it requires a soldering iron and spare chips to > > fix it.
John, do the math: for the current chips (single level cells), life is of order 10^5 cycles. So you have 10^5 gigabytes of writing. This takes *a long* time. Swapping is not an insane idea, once you have wear leveling. We don't do it now because JFFS2 cannot support swapping, and we don't have a wear level beneath the file system. UBI and Ubifs fix this, and it is something we can consider. > > > > Well, maybe it's not as bad as all that. When the NAND wears out, then > you can buy the SD card, thus deferring that purchase and taking > advantage of Moore's law in the interim. Lots of people tend to forget, however, that warm (and/or cold) salt air is a serious issue in many of the places we have to go. Any connector tends to die under these circumstances. > > Note that I'm not advocating in favor of soldered NAND - in fact I've > been one of the leading proponents of migrating to an SD-based storage > solution. I'm just pointing out that, if you're willing to buy an SD > card now (which is necessary for the SD-based swap solution), then you > are probably willing to buy one later. > Soldered down SD, however may be an intermediate point; may fewer wires than a conventional chip. -- Jim Gettys <j...@laptop.org> One Laptop Per Child _______________________________________________ Devel mailing list Devel@lists.laptop.org http://lists.laptop.org/listinfo/devel