I have a server with 2 SSDs:Model Family:     Intel 520 Series SSDsDevice Model:     INTEL SSDSC2BW240A3FFirmware Version: 400iUser Capacity:    240,057,409,536 bytes [240 GB]Sector Size:      512 bytes logical/physicalOn them I have 3 mdraid mirror devices (md0,1,2) formatted with EXT4 filesystem. I'm using mbr (not gpt) partition table. All 3 filesystems are mounted with discard mount option. /dev/md0 on / type ext4 (rw,discard,errors=remount-ro)/dev/md2 on /vservers type ext4 (rw,discard)/dev/md1 on /var type ext4 (rw,discard)The PROBLEM is that whenever I reboot the server, fstrim -v /any_mountpoint says it needed to trim ALL of the unused space. Once I do the full fstrim of the filesystems, everything works as expected until the next reboot. Running fstrim after a reboot again trims the whole filesystem.Could somebody explain to me what I'm doing wrong? I thought ext4 remembered the already trimmed parts of filesystem (on my desktop with 1 ssd, it does). This is on Ubuntu 14.04 with 3.13.0-23-generic kernel. 
Why does fstrim trim all of the free space on my mdraid mirror after a reboot?
ubuntu;ext4;raid;ssd;trim