Marc Joliet posted on Mon, 14 Jan 2019 12:35:05 +0100 as excerpted: > Am Montag, 14. Januar 2019, 06:49:58 CET schrieb Duncan: > [...] >> Unless you have a known reason not to[1], running noatime with btrfs >> instead of the kernel-default relatime is strongly recommended, >> especially if you use btrfs snapshotting on the filesystem. > [...] > > The one reason I decided to remove noatime from my systems' mount > options is because I use systemd-tmpfiles to clean up cache directories, > for which it is necessary to leave atime intact (since caches are often > Write Once Read Many). Thanks for the reply. I hadn't really thought of that use, but it makes sense... FWIW systemd here too, but I suppose it depends on what's being cached and particularly on the expense of recreation of cached data. I actually have many of my caches (user/browser caches, etc) on tmpfs and reboot several times a week, so much of the cached data is only trivially cached as it's trivial to recreate/redownload. OTOH, running gentoo, my ccache and binpkg cache are seriously CPU-cycle expensive to recreate, so you can bet those are _not_ tmpfs, but OTTH, they're not managed by systemd-tmpfiles either. (Ccache manages its own cache and together with the source-tarballs cache and git-managed repo trees along with binpkgs, I have a dedicated packages btrfs containing all of them, so I eclean binpkgs and distfiles whenever the 24-gigs space (48-gig total, 24-gig each on pair-device btrfs raid1) gets too close to full, then btrfs balance with -dusage= to reclaim partial chunks to unallocated.) Anyway, if you're not regularly snapshotting, relatime is reasonably fine, tho I'd still keep the atime effects in mind and switch to noatime if you end up in a recovery situation that requires writable mounting. (Losing a device in btrfs raid1 and mounting writable in ordered to replace it and rebalance comes to mind as one example of a writable-mount recovery scenario where noatime until full replace/rebalance/scrub completion would prevent unnecessary writes until the raid1 is safely complete and scrub-verified again.) -- Duncan - List replies preferred. No HTML msgs. "Every nonfree program has a lord, a master -- and if you use the program, he is your master." Richard Stallman
