I have a HP DL320e g8 v2 server running CentOS 7.1 (kernel 3.10.0-229.4.2.el7.x86_64). This server comes with a B120i onboard SmartArray controller, and it was configured with two identical 3TB Seagate disks in RAID-0. I've installed CentOS 7.1 minimal system, with XFS and bs=4096.
After system´s installation, I got theses rates to read and write:
dd if=/dev/zero of=test.img bs=4k count=2560000 2560000+0 records in 2560000+0 records out 10485760000 bytes (10 GB) copied, 25.4219 s, 412 MB/s dd if=test.img of=test2.img bs=4k 2560000+0 records in 2560000+0 records out 10485760000 bytes (10 GB) copied, 413.832 s, 25.3 MB/s dd if=test.img of=/dev/null bs=4k 2560000+0 records in 2560000+0 records out 10485760000 bytes (10 GB) copied, 400.053 s, 26.2 MB/s
As you can see, the WRITE rate is fast (about 400 MB/s), but the READ rate is very slow (about 25 MB/s). I've done two tests, first writing to another file and after writing to /dev/null... and in both cases the read rate is slow.
I get the same 25 MB/s read rate when coping a file from this server to another via NFS.
Somebody has any ideia about what could be happening?
I've tried using CentOS 6.6 and got the same results. This server will be a backup (bacula) server, and the disk read rate impacts the bacula performance...