Hi, On Tue, Apr 13, 2010 at 3:36 AM, Charles Manning <[email protected]> wrote: > You'd probably do far better to ask questions like this on the linux-mtd list > or similar.
Thanks. Will be heading there. > > I'm the author of the yaffs file system, so I can answer some of your > questions though. > > Pretty much all flash file systems or flash management layers such as UBI > perform at least some degree of wear levelling. This means that there is some > sort of logical to physical, or other, policy so that the writes don't happen > in the same place. That means those writes to a certain file will end up > being spread across many different blocks, thus meaning that writes to one > particular file won't wear out one part of flash. Read a bit about this on the wikipedia entry on Flash devices. On an embedded device based on linux where changes in files are done by the system itself (and not a user adding or deleting files), where these changes are not so much. Is it always a good idea to move certain files that change in a ramfs. Regards ~Sameer > > And yes, the endurance depends on the type of flash. Some are of the order of > 10^6, some are only 10^3. > > Worst I've seen is 10^2, but that was for a "bootloader" section and not > designated for file usage. > > -- CHarles > > On Tuesday 13 April 2010 07:58:22 Cathey, Jim wrote: >> I was concerned enough that our "/" fs is read-only, >> with symlinks for everything interesting down into >> /tmp/etc instead. The rcS script made the initial >> set from a bunch of template files. >> >> It, of course, was an embedded device that happened >> to be based on Linux, not some sort of "embedded Linux" >> device where J. Random Developer would expect to function >> happily. >> >> Last I heard, the worst of the NAND flash devices was >> on the order of 10^3-10^5 writes, not 10^6. >> >> -- Jim >> >> -----Original Message----- >> From: [email protected] [mailto:[email protected]] >> On Behalf Of Sameer Naik >> Sent: Monday, April 12, 2010 12:03 PM >> To: BusyBox Developer List >> Subject: NAND Write operations >> >> Hi, >> This may not be the right place to ask this question, but i only ask >> this because i believe most of the developers on this list work >> primarily with embedded systems. So here goes it. >> >> Normally on a linux system network configuration related files like >> resolv.conf and ifcfg-eth*, etc are stored in the /etc folder. These >> files are normally updated at boot or precisely when the network is >> configured. NAND memory have a ~100K write cycles before which write >> could start failing. >> This number is rather very large, hypothetically even if the network >> is configured 10 times a day the flash is good for around 27 years >> (100000 / (365 * 10)). >> >> Secondly, considerable amount of fragmentation could occur due to >> small updates on the file system >> >> I may be getting a little paranoid here, but how much is this of >> cencern on a production system. >> >> Regards >> ~Sameer >> _______________________________________________ >> busybox mailing list >> [email protected] >> http://lists.busybox.net/mailman/listinfo/busybox >> _______________________________________________ >> busybox mailing list >> [email protected] >> http://lists.busybox.net/mailman/listinfo/busybox > > > _______________________________________________ > busybox mailing list > [email protected] > http://lists.busybox.net/mailman/listinfo/busybox > _______________________________________________ busybox mailing list [email protected] http://lists.busybox.net/mailman/listinfo/busybox
