Hi,
I have a strange phenomenon that I cannot readily explain so I wonder if
anyone here can shed a light on this.
The host system is a Dell r815 with 64 cores and 256G ram and has centos
6 installed. The five guests are also running centos 6 and are running
as a hadoop cluster. The problem is
I experienced similar issues when disk images of virtual machines were
stored in qcow/qcow2 files instead of logical volumes (LVM).
Using LVM gives you way better I/O performace than using qcow files.
Also very important: when you partition your disk drive(s) make sure
that partitions are
What helped a lot for me is to increase the read ahead drastically on
guests:
# Set read-ahead for optimal disk I/O
blockdev --setra 16384 /dev/vda
I optained this value by repeatedly timing copies and this was, for my
installation at least, optimal.
