> Most subvolumes can be mounted with noatime, except for /home where I frequently need to sort files by modification time.
That doesn't sound right. Noatime turns off recording of the last access time, not modification.
That doesn't sound right. Noatime turns off recording of the last access time, not modification.
This noatime thing is an old-wive's tale that needs to die.
AFAIK, most "modern" filesystems (XFS,BTRFS etc.) all default to relatime
relatime maintains atime but without the overhead
EDIT TO ADD:
Actually,I've just done a bit of searching .... relatime has been the kernel mount default since >= 2.6.30 ! [1]
[1] https://kernelnewbies.org/Linux_2_6_30 (scroll to 1.11. Filesystems performance improvements)
The cost of atime is an extra write every time you read something.
Relatime changes this to one atime update per day (by default), low enough that it usually doesn't matter.
However, that update per day may have significant impact when you are using Copy-on-Write filesystems (btrfs, zfs). Each time the atime field is updated you are creating a new metadata block for that file. Old blocks can be reclaimed by the garbage collector (at an extra cost), but not if they exist in some snapshot.
All of this means that if you use btrfs/zfs and have lots of small files and take snapshots at least once per day, there's a noticeable performance difference between relative and noatime.
I've been using noatime everywhere for several years and I've never noticed any downside. This is definitely my recommended solution.
I've used noatime by default, except for few cases where I know it is used, in professional settings for probably two decades. Hopefully you know what kind of appliciation you are running. There are many parameters in a system and this is just one of them.
The only times I've seen atime used has been for a two queues, and only in the case of "has this file changes since last it was read". And that is precisely what relatime is for, the daily update is just an optional extra.