Rafael Skodlar wrote: > Jon Elson wrote: > >>AKSYS Tech Pty Ltd wrote: >> >> >>>Hi Guys >>> >>> >>> >>>Thanks very much for all the info. >>> >>>I must confess that this is my first time playing with Linux so it is >>>all a bit new to me. >>> >>>I am trying to make a solid “Industrial” controller, because as a day >>>job I retrofit and repair CNC machine tools. And as a result of this I >>>see many hard drive failures on the variety of PC based systems that I >>>get asked to fix. The DOS based units with the Disk-On-Chip modules are >>>very good and I have never had any problems with them. I have seen a >>>variety of methods of mounting HDD to try and eliminate the problems >>>with vibration. One company used to mount the HDD with a spring in each >>>corner and suspend the HDD like a spider in a web. So……… I would like to >>>go the solid state route. >>> >> >> >> >>>But if the number of read/write times is limited, possibly this isn’t >>>the best route to follow. >>> >> >>If the flash has a wear-leveling scheme that remaps the >>heavily-written sectors to new locations periodically, then the >>wear is a much less serious problem. Still, a system that >>rewrites the home block every minute, for instance, could wear >>the flash out in as little as 10 days without wear levelling, or >>in a couple months with it. >> >>If you buy top-line (Maxtor, Western Digital, etc.) hard drives >>that are not the latest-greatest capacity, in other words stable >>mature technology, and if you keep them cool and don't rattle >>them, they can last 10+ years. I think the spring suspension is >>likely to be a good idea. Temperature is also important, and >>many drives cook along at 50 C in PCs, which can't be good for them. >> >>Yes, I would like to see affordable, reliable solid state disks >>that didn't have some of these problems. Probably, it would be >>possible to modify one of the existing Linux file systems to >>take best advantage of a flash disk. If you could mount a flash >>drive read-only, that would stop all writes to the drive, which >>would fix the wear problem. Linux will run with the entire boot >>file system mounted read-only, as I understand it. It can also >>run with a heck of a lot of the rest of the traditional OS files >>moved to a read-only file system. All of >><anything>/bin/<anything>, and the same for /lib, /etc and some >> > > > /etc is not a candidate for RO. /etc has to be writable if you want to > change any user's password, connect to the net using DHCP, or do other > things that require automatic config change. Also, /etc/mtab changes > every time you mount or unmount something. Therefor /etc should be a > link to a rewritable device, either a disk or RAM. > Right, for these things you'd have to remount it RW. I was just thinking of ways to move as much as possible to a RO file system to prevent wearout of the flash chips. > Years ago when technology kept improving existing technologies not just > replacing them, floppy drives grew up to 120 and 240 MB capacity. The > advantage was in backward compatibility and it's capacity was good > enough for a good size Linux system like DSL etc. Unfortunately the > marketing never managed to get it of the ground to find them in stores > but you can still buy silly 1.4MB drives. > You can STILL boot a decent Linux kernel from a 1.44 Mb floppy, but that is not a reliable way to build a harsh-environment computer. > 120 or 240 MB would be enough to use as a rewritable portion of the > system. I have a 120MB version and it's reliable. > > BitMicro makes good solid state drives but only guys that build UAVs, > F-16s, etc. can afford them. However, prices might come down soon since > Dell started to sell a laptop model with an option to select a solid > state drive. > I've been waiting for these to become reasonable for years, I'm still waiting. But, they are getting closer. The wearout cycles on flash memory is improving, too, and there are some ferroelectric RAM technologies that will have wearout in the billion cycle range, but they are not anywhere as dense as flash yet. > USB drives with DOS format have one advantage, they only use write cycle > when you write a file to it. EXT3 and other similar file systems use and > change journaling and other information on partitions which makes it > hard for use with flash memory. right.
Jon ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2005. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
