https://www.architecting.it/blog/wekaio-matrix-performance-das/
On Tue, 9 Jun 2020 at 21:52, Ken Smith via GLLUG <[email protected]> wrote: > Hi All, > > While in lockdown I decided to do some performance testing on KVM. I had > believed that passing a block device through to a guest rather than > using a QCOW2 file would get better performance. I wanted to see whether > that was true and indeed whether using iSCSI storage was any better/worse. > > My test hardware is quite modest and this may adversely have affected > what I measured. The processor is a Intel Core2 6300 @ 1.86GHz with > VT-X support. It shows 3733 Bogomips at startup. There's 8GB RAM and an > Intel 82801HB SATA controller on a Gigabyte MB. The disks are two 3TB > SATA 7200RPM set up with a Raid 1 LVM Ext3 partition as well as other > non-Raid partitions to use to test. > > I used Fedora 32 as the KVM host and my testing was with Centos 8 as a > guest. > > On the host I got 60MB/s write and 143 MB/s read on Raid1/LVM/Ext3. I > wrote/read 10GB files using dd. 10Gb so as to overflow any memory based > caching. Without LVM that changed to 80 MB/s write and 149 MB/s read. > > I tried all kinds of VM setups. Normal QCOW2, pass though of block > devices Raid/LVM and Non-Raid/LVM. I consistently got around 14.5 MB/s > write and 16.5 MB/s read. Similar figures with iSCSI operating from both > file based devices and block devices on the same host. The best I got by > tweaking the performance settings in KVM was a modest improvement to 15 > MB/s write and 17 MB/s read. > > As a reference point I did a test on a configuration that has Centos 6 > on Hyper-V on an HP ML350 with SATA 7200 rpm disks. I appreciate that's > much more capable hardware, although SATA rather than SAS, but I > measured 176 MB/s write and 331 MB/s read. That system is using a file > on the underlying NTFS file system to provide a block device to the > Centos 6 VM. > > I also tried booting the C8 guest via iSCSI on a Centos6 Laptop, which > worked fine on a 1G network. I measured 16.8 MB/s write and 23.1 MB/s > read that way. > > I noticed an increase in processor load while running my DD tests, > although I didn't take any actual measurements. > > What to conclude? Is the hardware just not fast enough? Are newer > processors better at abstracting the VM guests with less performance > impact? What am I missing?? > > Any thoughts from virtualisation experts here most welcome. > > Thanks > > Ken > > > > -- > This message has been scanned for viruses and > dangerous content by MailScanner, and is > believed to be clean. > > > -- > GLLUG mailing list > [email protected] > https://mailman.lug.org.uk/mailman/listinfo/gllug
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