From mboxrd@z Thu Jan 1 00:00:00 1970 From: pwaechtler@mac.com (Peter =?iso-8859-15?q?W=E4chtler?=) Date: Wed, 13 Apr 2011 20:35:55 +0200 Subject: since when does ARM map the kernel memory in sections? In-Reply-To: References: <201104122052.17453.pwaechtler@mac.com> <201104130851.17676.pwaechtler@mac.com> Message-ID: <201104132035.55362.pwaechtler@mac.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Am Mittwoch, 13. April 2011, 17:44:09 schrieb Nicolas Pitre: > On Wed, 13 Apr 2011, Peter W?chtler wrote: > > Am Dienstag, 12. April 2011, 21:20:14 schrieb Andrei Warkentin: > > > How are you mounting your rootfs and what file system are you using? > > > What sort of corruptions to the super block are you seeing? > > > > It's using ext4 with metadata journalling in ordered mode. > > I had to check "if it's the FS" - the test programs create lots of > > directories and files while a timer is armed to issue a soft reset. > > The partitions where the "stress tests" run on - survive it happily - > > just the rootfs where almost nothing gets written is severly damaged so > > that fsck.ext4 will not repair it automatically. > > SD cards are doing their own wear leveling internally and you have no > control over it. Some blocks of data may be moved around, affecting a > separate logical partition, even if you are not actively writing to that > partition. Now if you cut power or reset the card while this is > happening you'll certainly end up with data loss. Those SD cards are > made to be both cheap and fast, meaning they're certainly not reliable > with regards to unexpected interruptions. > > Furthermore, you should have a look at this article and referenced > material: http://lwn.net/Articles/428584/. > > Yes, I know this article - and I know about wear levelling etc. Data loss is not the biggest problem. The capacity is huge (>>4GB) - therefore I wouldn't want to miss journalling - but I was not involved on the decision. Ten years ago I carefully ordered the fsync, rename on ext2 on a 64MiB CompactFlash - worked well enough. The vendor knows about the requirements - perhaps learned it with another customer ;) I tried to "smash" the FS without success in the past - but the rootfs was mounted via NFS ;) And the partitions that get tortured stay intact - of course you can say that the wear levelling switches some blocks - but I don't buy it. Thanks for all the nice work on Linux - Russell included ;) Peter