software raid settings and ext4

[Miguel González <miguel_3_gonzalez@yahoo.es>]

Hi,

 I´m running Proxmox 4.2 which is debian jessy with a software RAID of 2
Tb SATA disks of 7200 RPM in a dedicated server.

  I have set it up using OVH Proxmox installer with ext4. I have
realized that another server with just one SATA disk has writes of about
140 MB/s while this server with 2 disks has just reads around 40 MB/s:

  root@myserver:~# hdparm -Tt /dev/sda

/dev/sda:
 Timing cached reads:   11800 MB in  2.00 seconds = 5903.84 MB/sec
 Timing buffered disk reads: 136 MB in  3.17 seconds =  42.94 MB/sec

root@myserver:~# hdparm -Tt /dev/md4

/dev/md4:
 Timing cached reads:   11356 MB in  2.00 seconds = 5682.49 MB/sec
 Timing buffered disk reads: 132 MB in  3.10 seconds =  42.52 MB/sec

 root@myserver:~# pveperf /vz/
CPU BOGOMIPS:      42669.12
REGEX/SECOND:      935261
HD SIZE:           1809.50 GB (/dev/mapper/pve-data)
BUFFERED READS:    94.56 MB/sec
AVERAGE SEEK TIME: 17.88 ms
FSYNCS/SECOND:     10.15
DNS EXT:           16.93 ms
DNS INT:           23.36 ms (ibertrix-node2)


from specs from the manufacturer average seek time is around 8 ms

writes on the other hand seem to be fine:

root@myserver:~# dd if=/dev/zero of=/mytempfile
^C15210305+0 records in
15210305+0 records out
7787676160 bytes (7.8 GB) copied, 52.1116 s, 149 MB/s


performance from a VM (I have 5 VMs running in this 32 Gb RAM server)
running Centos 6.8:

root@vm [~]# dd if=/dev/zero of=/mytempfile
^C9360176+0 records in
9360176+0 records out
4792410112 bytes (4.8 GB) copied, 112.571 s, 42.6 MB/s

root@vm [~]# hdparm -Tt /dev/sda

/dev/sda:
 Timing cached reads:   7778 MB in  2.00 seconds = 3892.00 MB/sec
 Timing buffered disk reads: 122 MB in  3.59 seconds =  34.02 MB/sec



 I´m running 4.4.15-1-pve kernel.

 Is there any way to improve the performance of ext4 both in the hosting
proxmox server and the virtual machines?

 Regards,