Hi all, I have a btrfs setup of 4x2TB HDDs for /home in btrfs RAID0 on Ubuntu 15.10 (kernel 4.2) and btrfs-progs 4.3.1. Root is on a separate SSD also running btrfs.
About 6 people use it via ssh and run simulations. One of these simulations generates a lot of intermediate data that can be discarded after it is run, it usually ends up being around 100GB to 300GB spread across dozens of files 500M to 5GB apiece. The problem is that, when it comes time to do a "rm -rf ~/working_directory" the entire machine locks up and sporadically allows other IO requests to go through, with a 5 to 10 minute delay before other requests seem to be served. It can end up taking half an hour or more to fully remove the offending directory, with the hangs happening frequently enough to be frustrating. This didn't seem to happen when the system was using ext4 on LVM. Is there a way to fix this performance issue or at least mitigate it? Would using ionice and the CFQ scheduler help? As far as I know Ubuntu uses deadline by default which ignores ionice values. Alternatively, would balancing and defragging data more often help? The current mount options are compress=lzo and space_cache, and I will try it with autodefrag enabled as well to see if that helps. For now I think I'll recommend that everyone use subvolumes for these runs and then enable user_subvol_rm_allowed. Regards, Mitch Fossen -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
