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KVM host SSD optimization, cache, io, x-data-plane parameters questions
Hello,
currently i have installed CentOS 6.9 64bit 2.6.32-042stab123.9 (vzkernel)
and enabled Multi virtualization (thru Virtualizor) so i can run also KVM. It does not works well.
Which KVM parameters (cache, io, iothreads, x-data-plane) you are using or advise for good performance please?
In my case i have SSD Raid 10, LSI 9210-8i RAID Controller card does NOT feature any BBU nor cache, probably not TRIM.
I can set these in Virtualizor:
"I/O Policy" can be: Native or Threads
"Disk Caching" can be Writeback, Writethrough, Direct Sync, Default
I read that Writeback is recommended because increased speed.
Here someone mentions this combination:
cache=directsync
io=native
x-data-plane=on (now known as iothreads)
my current KVM .xml file contains:
https://pastebin.com/jZpRjEvw
Regarding SSD optimizations, so far i added vm.swappiness to the /etc/sysctl.conf
(vm.swappiness=10) , then sysctl -p
enabled "issue_discards" in /etc/lvm/lvm.conf
it issue discards to PVs that are no longer used by an LV (i use LV, trying Thin LVM LVs)
Do i need to enable such setting anyhow also inside in KVM .xml configuration file? and i added "10 10 */7 * * /usr/bin/ionice -n7 /sbin/fstrim /vz" to the crontab?
Here is advised: "Use VirtIO drivers (IDE emulation does NOT scale beyond 1 thread)" anyone can confirm this? Here on page 16 is mentioned how to enable virtio-blk-data-plane:
Here is the code:
https://pastebin.com/pSPEEU6s
Virtio vs IDE: https://kparal.wordpress.com/2012/09/12/kvm-disk-performance-ide-vs-virtio/
Did anyone tested? which combination and additional tweaks do you recommend?
Comments
Why enable writeback you dont have bbu or cache for your raid card