Hi, I have the problem with fstrim (thin provisioning). some details: uname -a Linux test.local 2.6.32-279.14.1.el6.x86_64 #1 SMP Tue Nov 6 23:43:09 UTC 2012 x86_64 x86_64 x86_64 GNU/Linux mount /dev/mapper/VolGroup00-lv_root on / type ext4 (rw) proc on /proc type proc (rw) sysfs on /sys type sysfs (rw) devpts on /dev/pts type devpts (rw,gid=5,mode=620) tmpfs on /dev/shm type tmpfs (rw) /dev/md0 on /boot type ext4 (rw) none on /proc/sys/fs/binfmt_misc type binfmt_misc (rw) /dev/mapper/VolGroup00-lv_test1 on /mnt/test1 type ext4 (rw) /dev/mapper/VolGroup00-lv_test2 on /mnt/test2 type ext4 (rw) /dev/mapper/VolGroup00-lv_test5 on /mnt/test5 type xfs (rw) df -h Filesystem Size Used Avail Use% Mounted on /dev/mapper/VolGroup00-lv_root 20G 2.3G 17G 13% / tmpfs 1.6G 0 1.6G 0% /dev/shm /dev/md0 99M 27M 67M 29% /boot /dev/mapper/VolGroup00-lv_test1 40G 2.6G 35G 7% /mnt/test1 /dev/mapper/VolGroup00-lv_test2 4.0G 1.2G 2.6G 32% /mnt/test2 /dev/mapper/VolGroup00-lv_test5 3.0G 725M 2.3G 24% /mnt/test5 lvs -a -o+metadata_percent LV VG Attr LSize Pool Origin Data% Move Log Copy% Convert Meta% lv_native VolGroup00 -wi-a--- 5.00g lv_root VolGroup00 -wi-ao-- 20.00g lv_swap VolGroup00 -wi-ao-- 4.00g lv_test1 VolGroup00 Vwi-aotz 40.00g thin_pool 27.73 lv_test2 VolGroup00 Vwi-aotz 4.00g thin_pool 98.61 lv_test5 VolGroup00 Vwi-aotz 3.00g thin_pool 45.40 thin_pool VolGroup00 twi-a-tz 100.00g 16.40 8.47 [thin_pool_tdata] VolGroup00 Twi-aot- 100.00g [thin_pool_tmeta] VolGroup00 ewi-aot- 100.00m This test server (CentOS 6.3 - not install from scratch). I was updated this server from 6.2 version: last | tail -3 reboot system boot 2.6.32-220.el6.x Mon Jan 23 16:03 - 16:04 (00:01) wtmp begins Mon Jan 23 16:03:26 2012 I test only ext4 fs partitions. When I used fstrim I had next error: fstrim /mnt/test1 fstrim: /mnt/test1: FITRIM ioctl failed: Operation not supported I want retrieve free space from the ext4 fs to the total free space of thin_pool after delete files on the ext4 fs (lv_test1).I will have more free space for another thin LV. Is it possible to get it? Thanks in advance.