On 10/15/2015 09:19 AM, Nicholas Leippe wrote: > Is bit flipping on storage media really a valid concern? > My understanding of signal storage media is that at the lowest levels there > are significant amounts of ECC already in place to handle imperfections in > the media itself. Sectors that are detected as deteriorating are remapped > before the data can no longer be read--thus the source of the S.M.A.R.T. > "grown defects" counter. For SSDs, maybe this concern is now raising its > ugly head again?
I think it could be a concern. I don't think it's possible to reliably detect them with SMART features. And when they do happen, without FS checking blocks for checksums or hashes, they will be completely silent corruptions. I've been carrying with data with me for nearly 30 years, continuously copying my data from media to media as I went along. Given the unreliable nature of yesterday's magnetic removable media, I'd be surprised if there isn't the odd bit flipped in my data somewhere. It's true things are much more reliable and self-correcting now. So maybe it wouldn't matter. > <snip> > IMO, ext4 is the safest fs choice in Linux land today. Btrfs is simply not > ready yet. XFS while fairly mature still has some weird behaviors reported > occasionally, and ZFS while feature-full--and for which may be your cup of > tea--can be a little more effort to deal with. I agree for the most part. I've been using BtrFS for nearly four years with very few issues and no apparent corruption. Being ready is entirely a subjective measure. If everyone waits for some magical threshold of "ready" then it can never quite get there. ZFS definitely has a learning curve. But once you get on to it, it's hard to go back to other file systems. Nearly free snapshots is just so addicting and powerful. When I worked at BYU our main file server was ZFS and for backups we'd snapshot all the file systems first, and then backup from the snapshot since the backup took much of the night. This way we got a more coherent backup from a moment in time. Also we'd snapshot home directories hourly, daily, monthly, and sometimes yearly. No more calls from users saying I deleted a file this morning can you recover it from backup for me? /* PLUG: http://plug.org, #utah on irc.freenode.net Unsubscribe: http://plug.org/mailman/options/plug Don't fear the penguin. */
