On Wed, May 28, 2014 at 11:26 AM, Bob Sanders <rsand...@sgi.com> wrote: > Marc Joliet, mused, then expounded: >> Am Tue, 27 May 2014 15:39:38 -0700 >> schrieb Bob Sanders <rsand...@sgi.com>: >> >> While I am far from a filesystem/storage expert (I see myself as a mere >> user), >> the cited threads lead me to believe that this is most likely an >> overhyped/misunderstood class of errors (e.g., posts [1] and [2]), so I would >> suggest reading them in their entirety. >> >> [0] http://comments.gmane.org/gmane.comp.file-systems.btrfs/31832 >> [1] http://permalink.gmane.org/gmane.comp.file-systems.btrfs/31871 >> [2] http://permalink.gmane.org/gmane.comp.file-systems.btrfs/31877 >> [3] http://comments.gmane.org/gmane.comp.file-systems.btrfs/31821 >> > > FWIW - here's the FreeNAS ZFS ECC discussion on what happens with a bad > memory bit and no ECC memory: > > http://forums.freenas.org/index.php?threads/ecc-vs-non-ecc-ram-and-zfs.15449/ >
I don't think that anybody debates that if you use btrfs/zfs with non-ECC RAM you can potentially lose some of the protection afforded by the checksumming. What I'd question is that this is some concern unique to btrfs/zfs. I'd think the same failure modes would all apply to any other filesystem. So, the message should be that ECC RAM is better than non-ECC RAM, not that those who use non-ECC RAM are better off using ext4 instead of zfs/btrfs. I'd think that any RAM-related issue that would impact zfs/btrfs would affect ext4 just as badly, and with ext4 you're also vulnerable to all the non-RAM-related errors that checksumming was created to solve. If your RAM is bad then all kinds of stuff can go wrong. Ditto for your cache memory in the CPU, logic circuitry in the CPU, your busses, etc. Most systems are not fault-tolerant of these system components and the cost to make them fault-tolerant tends to be fairly high. On the other hand, the good news is that you're far more likely to have problems with data stored on a disk than in RAM, which is probably why we haven't bothered to improve the other components. Rich
