[OmniOS-discuss] horrible disk performance under KVM

[ashley willis]

I have 14GB dump of a MongoDB database that took 10 minutes to restore
on bare metal OmniOS -- I'm fine with this (system is an 8-core AMD
FX-8150, 32GB ram, pair of 500GB WD 'blue" drives mirrored, 90GB ssd
cache -- all desktop-grade).

Running OmniOS under KVM on this box, the same operation took 246
minutes with the dump available over an NFS share from the bare metal
system (given 2 cores, 2GB ram, and a 30GB zvol).

Under the same KVM instance, I decided to see the performance reading
the dump from NFS and having the MongoDB data directory on this same
NFS share, and it's on track to finish in under 60 minutes (half-way
done). That's more than 4 times faster.

What gives?

/usr/bin/qemu-system-x86_64 -name OmniOS_Text_r151006p.iso -enable-kvm
-vnc 0.0.0.0:15 -smp 2 -m 2048 -no-hpet -localtime -drive
file=/dev/zvol/rdsk/rpool/omnios,if=ide,index=0 -net
nic,vlan=0,name=net0,model=e1000,macaddr=2:8:20:e:15:33 -net
vnic,vlan=0,name=net0,ifname=vnic10,macaddr=2:8:20:e:15:33 -vga std
-daemonize

-ashley