I have a server with Ubuntu 12.04 as host OS with a single RHEL4 KVM guest
running. At this point, I cannot upgrade that RHEL4 OS to any later version.
Since there is no virtio support in the guest's kernel, I'm stuck with IDE
emulation. And it is so sssslllloooowwww.
The guest machine is running MaxDB/SAPDB and executing CHECK DATA command which
checks the entire database for data corruption. The db's size is somewhere
between 200GB and 250GB. While it is running the data check in tty0, it is
also running vmstat in tty1 and vmstat is showing a 1-minute (i.e. "vmstat 60")
average of 75% iowait.
Simultaneously, I'm running vmstat also in the host OS, and it is only showing
a 8%-10% iowait average.
Are there any particular tweaks I can do to improve upon the guest's iowait?
Bring it as close as possible to the host's. I already have io=native set.
--- mike t.
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