Very interesting discovery that GT1 pointed out:
A disk partition:
/dev/sda1 on / type ext4 (rw,noatime,nodiratime,discard,data=ordered,errors=remount-ro)
CPU BOGOMIPS: 32549.58
REGEX/SECOND: 1280800
HD SIZE: 9.18 GB (/dev/sda1)
BUFFERED READS: 110.06 MB/sec
AVERAGE SEEK TIME: 0.31 ms
FSYNCS/SECOND: 272.49
DNS EXT: 59.21 ms
DNS INT: 1.05 ms (datanom.net)
/dev/sda1 on / type ext4 (rw,noatime,nodiratime,data=ordered,barrier=1,errors=remount-ro)
CPU BOGOMIPS: 32550.42
REGEX/SECOND: 1312899
HD SIZE: 9.18 GB (/dev/sda1)
BUFFERED READS: 112.57 MB/sec
AVERAGE SEEK TIME: 0.31 ms
FSYNCS/SECOND: 675.21
DNS EXT: 68.32 ms
DNS INT: 1.07 ms (datanom.net)
A LVM partition:
/dev/mapper/pve-data on /var/lib/vz type ext4 (rw,noatime,nodiratime,discard,data=ordered)
CPU BOGOMIPS: 32549.58
REGEX/SECOND: 1251371
HD SIZE: 88.59 GB (/dev/mapper/pve-data)
BUFFERED READS: 112.36 MB/sec
AVERAGE SEEK TIME: 0.28 ms
FSYNCS/SECOND: 274.38
DNS EXT: 65.60 ms
DNS INT: 0.94 ms (datanom.net)
/dev/mapper/pve-data on /var/lib/vz type ext4 (rw,noatime,nodiratime,data=ordered)
CPU BOGOMIPS: 32550.42
REGEX/SECOND: 1251491
HD SIZE: 81.70 GB (/dev/mapper/pve-data)
BUFFERED READS: 111.12 MB/sec
AVERAGE SEEK TIME: 0.28 ms
FSYNCS/SECOND: 781.10
DNS EXT: 65.11 ms
DNS INT: 1.00 ms (datanom.net)
Disk partition without discard increases fsyncs 3x
LVM partition without discard increases fsyncs 4x
Are there something wrong with the backported discard implementation in the current Redhat 2.6.32 kernel?????