[libvirt-users] How to best I/O performance for Window2008 and MSSQL guest VM

Roberto Fichera kernel at tekno-soft.it
Tue Dec 6 08:01:43 UTC 2016

On 12/06/2016 06:06 AM, Blair Bethwaite wrote:
> Hi Roberto,

Hi Blair

> What is the cpu and memory configuration of your guest? 

I've set to copy host configuration (16 cores) and memory is set to 24GB, host has 64GB.
Guest is Windows 2012 64bits version

Architecture:          x86_64
CPU op-mode(s):        32-bit, 64-bit
Byte Order:            Little Endian
CPU(s):                16
On-line CPU(s) list:   0-15
Thread(s) per core:    2
Core(s) per socket:    8
Socket(s):             1
NUMA node(s):          1
Vendor ID:             GenuineIntel
CPU family:            6
Model:                 79
Model name:            Intel(R) Xeon(R) CPU E5-2620 v4 @ 2.10GHz
Stepping:              1
CPU MHz:               1200.219
CPU max MHz:           3000.0000
CPU min MHz:           1200.0000
BogoMIPS:              4194.79
Virtualization:        VT-x
L1d cache:             32K
L1i cache:             32K
L2 cache:              256K
L3 cache:              20480K
NUMA node0 CPU(s):     0-15
Flags:                 fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr
sse sse2 ss ht tm pbe syscall nx pdpe1gb rdtscp lm constant_tsc arch_perfmon pebs bts rep_good nopl xtopology
nonstop_tsc aperfmperf eagerfpu pni pclmulqdq dtes64 monitor ds_cpl vmx smx est tm2 ssse3 sdbg fma cx16 xtpr pdcm pcid
dca sse4_1 sse4_2 x2apic movbe popcnt tsc_deadline_timer aes xsave avx f16c rdrand lahf_lm abm 3dnowprefetch epb
intel_pt tpr_shadow vnmi flexpriority ept vpid fsgsbase tsc_adjust bmi1 hle avx2 smep bmi2 erms invpcid rtm cqm rdseed
adx smap xsaveopt cqm_llc cqm_occup_llc cqm_mbm_total cqm_mbm_local dtherm ida arat pln pts
> Are you pinning to dedicated CPUs, 


> are you exposing host topology and cpu
> features, 


> do you have dedicated I/O threads? 

if you are talking about disk I/O, no. Should I do that?

> Are you backing the guest memory with hugepages? 

Don't know, how can I check or set it?

> All of the above will likely increase performance and minimise noise.
> Cheers,
> On 6 December 2016 at 05:13, Roberto Fichera <kernel at tekno-soft.it> wrote:
>> Hi There,
>> I've moved some Windows2012 with MSSQL VMs from an hold ESXi 5.5 machine
>> to a more recent and powerful machine running Fedora 24 x86_64 and related libvirt + KVM
>> virtualization. I've moved the VMs filesystem to LVM slices and installed the VirtIO drivers
>> in to all Windows VMs. I've also set both Disk and Network interface to work using VirtIO.
>> So far so good everything works pretty fine. Now I would like to tune at best the MSSQL VM
>> for both Disk and Network interfaces in order to get the best performance possible.
>> Regarding network interface I've set it to work as bridge instead to go through to macvtap, so I'm
>> not sure what is the best in this case.
>> Regarding disk, since it's LVM I've chosen to go to cache mode none and IO mode native. Also
>> here cannot judge what's the best setup for the workload. I'm undecided to use IO mode threads
>> along directsync cache mode.
>> Finally I've set "ionice -c 1 -p <qemu-pid> -n 0" and "renice -n -10 <qemu-pid>" for the interested
>> VM that I want to get best performance possible.
>> Even with the above setup, the MSSQL VM has performance similar to the old machine running
>> ESXi 5.5, so does anyone can suggest where too look at and/or what would be the right setup?
>> Thanks in advance.
>> Roberto Fichera
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