On Tue, Jan 7, 2020 at 6:41 PM Zygo Blaxell <ce3g8jdj@xxxxxxxxxxxxxxxxxxxxx> wrote: > > Consumer SD cards have been ruthlessly optimized for decades, mostly > for cost. It will take a while for the consumer-facing part of the > industry to dig itself out of that hole. In the meantime, we can expect > silent data corruption, bad wear leveling, and power failure corruption > to be part of the default feature set. I cackled out loud at this. > I run btrfs with dup data and dup metadata on the Pis, with minimized > write workloads (i.e. I turn off all the local log files, sending the > data to other machines or putting it on tmpfs with periodic uploads, > and I use compression to reduce write volume). I don't use snapshots on > these devices--they do get backups, but they are fine with plain rsync, > given the minimized write workloads. I haven't tried changing filesystem > parameters like node size. Dup data doesn't help the SD card last any > longer, but it does keep the device operating long enough to build and > deploy a new SD card. I use zstd:1, space_cache v2, and dsingle mdup. Curiously I've not seen any read errors on these. They just stop writing. I can mount and read from them fine, just writes file (silently on the USB sticks, kinda hilarious: yep, yep, i'm writing, no problem, yep, oh you want back what you just wrote, yeah no you get yesterday's data). > Samsung is making SD cards with 10-year warranties and a 300 TBW rating > (equivalent, it is specified in units of "hours of HD video"). They are > USD$25 for 128GB, 100MB/s read 90MB/s write. No idea what they're like > in the field, I start test deployments next week... Yeah the Samsung SD cards I have also are 10 year, but I have no idea what the TBW is and they don't report writes. EVO Plus, U3, is supposed to do 30M/s writes but no matter the file system I get 20MB/s out of it. I get a statistically significant extra ~350K/s with Btrfs. Reads are around 80-90M/s. Of course effective reads/writes is higher with compression. USB sticks I think are a few years warranty. -- Chris Murphy
