Unless I'm misinterpreting something it appears that maybe btrfs doesn't pass fstrim commands down to the underlying drives when being used in a RAID-1 config.
I have this output from a small script I wrote to run at boot time (and also via cron.weekly), rather than using continous trim in the boot options: # cat /var/log/trim.log Thu Oct 13 07:40:07 CDT 2016 /boot: 454 MiB (476062720 bytes) trimmed Thu Oct 13 07:40:08 CDT 2016 /: 8.9 GiB (9585152000 bytes) trimmed Thu Oct 13 07:40:22 CDT 2016 /btrfs/0: 0 B (0 bytes) trimmed /boot and / are mdraid RAID 1 on partitions 1 and 3 of two Samsung 850 Pro SSDs. /btrfs/0 is a btrfs-raid RAID 1 of partition 4 on the same two drives. The btrfs case does not seem to accomplish anything. By comparison, I have the same drive in my laptop, but just a single one, and the non-btrfs-raid-1 file system on one of its partitions does run fstrim successfully. This is quite possibly a known limitation, but I didn't find anything about it through some quick searching. Maybe I didn't dive deep enough... -- twalb...@gmail.com, twalb...@comcast.net -- 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
