Category Archives: linux

Running benchmark: Comparing Ubuntu 20.04 and RHEL 8.5 performance

The claim

I found a claim on Quora that Ubuntu is slow compared to RHEL. I never thought about it. Is it really? It seemed like a sentimental statement with nothing to prove it. I questioned the claim and found out, that many people tried to support the claim still without providing any kind proof.

Instead of continuing to asks any evidence, I decided to dig the evidence my self.

Is there any difference in the performance between the two? I don’t really know, but if you think about default server install with nothing extra, I doubt there could be any significant performance difference.

Ubuntu 20.04 has currently kernel 5.4 where as RHEL 8.5 has 5.13. Libraries and software are pretty much the same. File system by default is XFS on both. I always enable LVM although that could affect performance – certainly not by improving it, but there are other advantages. I don’t think LVM reduces performance much either and as said I always set it up anyway.

In this case I have two virtual machines both having 4GiB RAM and two 3.3GHz CPU cores running on qemu/kvm. The host OS is, yes you guessed right, Ubuntu 20.04 , because on desktop it has certain software I need. And, it works well as virtual host too. That does not affect the results anyhow, since the guest OS has no idea of host OS.

I haven’t tuned either of the guests OS at all except for one thing. I set tuned profile to virtual-guest for both, which makes sense. It is the recommended profile when I run tuned-adm recommend on both of the guests machines.

Put the HammerDB down

Last I ran HammerDB I had to settle with text based version, but this time it had a nice working GUI. But even before quick HammerDB installation, I downloaded Db2 11.5.7 Community Edition. Installed it on both Ubuntu and RHEL. I created SAMPLE database with db2sampl and took timing for that: no difference really. I knew it. Ok that doesn’t prove anything.

But, the real test does. HammerDB.

Ubuntu 20.04

Let’s start with Ubuntu. I read a tutorial on how to run time based benchmark with HammerDB. I want to do this fast. One virtual user only. Looks good.

Ubuntu 20.04

The process goes:

  • Choose Engine and configure it (Db2)
  • Build schema
  • Configure and load driver
  • Configure virtual user
  • Create virtual user(s)
  • Run virtual users
  • Monitor and wait
Here are the results for Ubuntu.

The results for Ubuntu 20.04

System achieved 5178 NPM from 22865 Db2 TPM

RHEL 8.5

Then same thing for RHEL. The machine crashes twice. Reminds me of kernel parameters. We have only 4GiB, so might be I need to tune them. But no, it run all good the third time. In my previous job though, servers with low memory running Db2 on RHEL crashed always without tuning the kernel parameters. There’s a simple formula based on RAM to calculate correct values for Db2 here. That said, I did not change anything from defaults for Ubuntu nor RHEL. It wouldn’t be fair comparison, if I started to tune the kernel parameters for one and not to the other.

Running on RHEL 8.5
There’s finally some I/O wait
The winner is RHEL 8.5 by two New Orders Per Minute (NOPM)

The results for RHEL 8.5

System achieved 5180 NOPM from 22815 Db2 Db2 TPM

First conclusion

There is really no difference between Ubuntu and RHEL what comes to achieved performance results. The two new orders per minute makes 0.04% difference which I’m pretty sure no one can notice just by “using the server a bit”.

Comparison between database engines

Since I already started playing with HammerDB, why not try some more tests. I have earlier installed Db2 on the host machine itself as well as MS SQL Server. I also have virtual machine running Oracle Linux 8 on it with the same 4GiB RAM and two CPU core setup. MySQL and PostgreSQL I have running on the host itself.

The hosts OS, as said, is running Ubuntu Desktop 20.04. It has 4 x 3.3GHz cores and 32GiB RAM and fast NVMe 500GiB M.2 PCIe SSD. This is small form factor machine suitable for industrial use as a headless server running for example Linux. Or you can use it as desktop computer as well. My idea for it was to use it as a platform for several virtual guests, but I wanted to see how it works as a Linux desktop computer as well.

Let’s do few quick tests on the host itself for various database engines. More of a test of HammerDB itself than real comparison between the engines.


TEST RESULT Ubuntu 20.04 Desktop: System Achieved 6651 NOPM from 2928 TPM.

I’m a bit surprised it didn’t achieve more. Need to test more. It takes time for bufferpools to warm up with automatic memory tuning and with 32GiB memory I’m pretty sure we could get much better results.

MS SQL Server

But let’s check with MS SQL Server I have running on the same machine. Certainly Db2 beat MS SQL Server, right?

MS SQL Server gets higher TPM numbers compared to virtual machines
Obviously the benchmark is somewhat different between the engines,

The winner is… oh no, MS SQL Server

8394 New Orders Per Minute with 19243 SQL Server TPM


I have one Oracle 21c Server running on VM running Oracle Linux 8. Oh but Oracle – I’m so lost with it. HammerDB asks too much questions and it seems I need to create another pluggable database. I will do that – later.

PostgeSQL and MySQL

Out of curiosity I ran the test for PostgreSQL and MYSQL:

PostgreSQL: TEST RESULT: 11607 NOPM from 26880 PostgeSQL TPM


I have no idea why the difference between above two is that significant. Might be for various reasons. I wouldn’t pay much attention on the difference since running the test on host OS and not on virtual machines with proper setup doesn’t make much sense – unlike the more serious comparison I did for Ubuntu Server and RHEL.

Final Conclusion

Without official test for Oracle we cannot make any other conclusion than Oracle is the slowest from these three DB Engines: Db2, MS SQL Server and Oracle. I’m kidding of course; I’m no Oracle expert and just too slow myself to set a proper test for Oracle. That might change once I have enough time to dig deeper on Oracle. For MySQL and PostgreSQL the test was also too quick; more of a test do they work similarly in comparison to Db2 and MS SQL what comes to HammerDB.

What comes to the original claim about Ubuntu being overall slow and which surprisingly many is willing to believe, I think I have busted the claim.

We can speculate how about real server environments and please do, but before you actually have any benchmarks to show otherwise, I take it proven that Ubuntu and RHEL are equally slow or fast.

Also, what comes to MS SQL Server performance compared to Db2, obviously this was not the last word. Let’s try with 10 virtual users beating Db2 for a bit longer.

Db2 with 10 Virtual Users

Final results for Db2 running on this tiny Asus Mini PC PN41 were:

TEST RESULT: System achieved 15650 NOPM from 68735 Db2 TPM.

So we have a winner: Db2 11.5.7?

In a sense Db2 won that it did get the highest number of new orders per minute yes. But in comparing with other database engines I didn’t really organise any meaningful tests between them this time.

Want to test yourself?

Prove me wrong. Run your own tests and provide me your data and conclusions. I have serious doubt Ubuntu Server and RHEL differs much what comes to performance. There certainly is plenty of other things which makes the difference when choosing the distribution. Things like support, cost, platform you are running on and so on. Red Hat certainly has it’s advantages on enterprise level support whereas Ubuntu started strong on desktop, but it is easy to deploy for example on Azure and fully supported.

Create Linux VM running CentOS 7.3 minimal with pyodbc and Netezza Client

This document describes how to create Linux Virtual Machine (VM) to be run on macOS or Windows Host. When followed the steps in this document, you will have CentOS 7.3 VM capable of running Netezza Linux Client, unixODBC, Python 3.6 with pyodbc and pandas among others. This setup is useful for developing Python code which needs Netezza connection.

Especially macOS users will benefit from this kind of setup, since there is no Netezza client for macOS.

This document concentrates on deploying the VM on VirtualBox, but the CentOS setup portion is identical also when using other hypervisors ie. VMWare Player, VMWare Workstation or VMWare Fusion.

Note: The LinuxVM created in this documented has all capabilities on Python 3.6. You execute python code calling python3.6 instead of just python, which points to python 2.75.

Install CentOS 7.3 on VirtualBox

  1. Download newest version of VirtualBox and install it:
  2. Once installed go to VirtualBox menu and choose “Preferences” and click “Network”.
  3. Click “Host-only Networks” and choose icon add: 
  4. Now you have new “Host-only Network” which is needed for incoming connections. You can check the details by double clicking vboxnet0:
  5. Next create VM with two network adapters:
    1. Choose “New” and select “Name”, “Type” and “Version”:
    2. Click continue. You can keep the memory on 1024MB which is the default.
    3. Click continue and choose “Create virtual hard disk now” and click “Create”.
    4.  “Hard disk type” can be VDI, if you do not plan to run VM on other hypervisors, but if you plan to run it on VMWare hypervisor, choose VMDK. Click “Continue”.
    5. For flexibility choose “Dynamically allocated” and for best performance choose “Fixed size”.
    6. For most purposes 8.0GB is enough, but your needs may vary. Choose “Create”.
    7. Now VM is created, but we need to change some of the network settings:
      1. While new VM is highlighted, choose “Settings” and select “Network” tab.
      2. “Adapter 1” default settings are ok for most cases, but we need to add “Adapter 2” so click “Adapter 2”. We need 2nd Network card for incoming connections, so we select “Enable Network Adapter” and set “Attached to: Host-only Adapter”:
      3. Click “OK”.
  6. We need to have CentOS minimal installation image which we can download from CentOS site:
  7. Choose your download site and store the image to desired location. We need it only during intallation.
  8. Once downloaded, go back to VM Settings on virtual box:
    1. Select “Storage” tab and “Controller: IDE” and click the CDROM icon and then another CDROM icon on right side from “Optical Drive” selection and “Choose Virtual Optical Disk File”.
    2. Select the CentOS minimal installation disk image you downloaded on previous step:

      1. Click “OK”
  9. Now we can start the CentOS minimal installation. Choose “Install….” when VM has booted.
  10. Next we get graphical installation screen. We can keep language settings as default and click “Continue”:
  11. Note when you click the VM, it will grab the mouse. To release the mouse, click left CMD (on MacOS).
  12. Click “Network & Host name”. You can specify your hostname as preferred.
  13. Both Network cards are off by default. Set them both to “ON”.
  14. For both Network cards, click “Configure” and on “General” tab choose “Automatically connect to this network when it is available”:
  15. Click “Done” to get out from Network settings, and click “Installation Destination” to confirm storage device selected by default is correct (no need to change anything). Then click “Done” to get back to main screen and you can start the installation by selecting “Begin Installation”.
  16. During installation set root password and select to create user. In my examples for setting up Netezza client, I have chosen to create “Netezza User” with username “nz”. I will also make this user an administrator:
  17. Once installation is done you can click “Finnish configuration” and then “Reboot”.
  18. VM boots now first time. You can either ssh to the system (from Terminal on MacOS, or using Putty on Windows).
  19. If this is only VM using Host-only network on VirtualBox, it’s likely the IP is You can check the IP for device enp0S8 with command: ip addr show when logged in through VirtualBox console.
  20. After installation first thing to do is to update all packages with yum update command. Either as root give command “yum -y update” or as administrative user as “sudo yum -y update”.

Configure file sharing between Host and Guest OS

You might want to be able to share, for instance your PycharmProjects folder to run Python code you developed directly on LinuxVM. That is a bit of the whole point for the LinuxVM in this case.

To achieve that, you need to enable file sharing. There is few additional steps needed I’l go through below:

  1. You need few additional packages first. Run following commands as root:
    1. yum -y update
    2. yum -y install gcc kernel-devel make bzip2
    3. reboot
  2. Once LinuxVM has rebooted and you have LinuxVM Window active select from menu “Devices” –> “Insert Guest Additions CD Image…” . Then log in to LinuxVM as root via VirtualBox console or ssh again and run following commands:
    1. mkdir /cdrom
    2. mount /dev/cdrom /cdrom
    3. /cdrom/
  3. Now select the folder you want to share from your Host OS to LinuxVM. Go to VM settings and choose “Shared Folders” tab and click icon and then choose the folder you want to share:
  4. Note: Make sure you set the mount permanent. No need for automount option, since we do it a bit differently below.
  5. Above we are sharing PycharmProjects folder. We want to have PycharmProjects folder mounted on LinuxVM on nz users home directory. As nz user we first create directory PycharmProjects with command: mkdir $HOME/PycharmProjects
  6. Then as root, we add following entry to /etc/fstab:PycharmProjects /home/nz/PycharmProjects vboxsf uid=nz,gid=nz           0 0
  7. After reboot you should now have your PycharProjects folder mounted with read and write access under nz users home directory.

    Note: The purpose for above share is, that when you develop your Python code with Pycharm on MacOS and if your code needs connection to Netezza, you can not run it on MacOS, since there is no Netezza drivers. Instead, when following this guide, you will be able to run you Pycharm edited code seamlessly on the LinuxVM through ssh connection, and once confirmed to work, you can commit your changes.

Install Python 3.6 with pyodbc, pandas and sqlalchemy

Log in to LinuxVM as root and run following commands:

yum -y update
yum -y install git
yum -y install yum-utils
yum -y groupinstall development
yum -y install
yum -y install python36u
yum -y install python36u-pip
yum -y install python36u-devel
pip3.6 install pandas
yum -y install unixODBC-devel
pip3.6 install pyodbc
yum -y install gcc-c++
yum -y install python-devel
yum -y install telnet
yum -y install compat-libstdc++-33.i686
yum -y install zlib-1.2.7-17.el7.i686
yum -y install ncurses-libs-5.9-13.20130511.el7.i686
yum -y install libcom_err-1.42.9-9.el7.i686
yum -y install wget
yum -y install net-tools
pip3.6 install sqlalchemy
pip3.6 install psycopg2

Testing pyodbc

Edit the connection string accordingly:

[nz@nzlinux ~]$ python3.6
Python 3.6.2 (default, Jul 18 2017, 22:59:34) 
[GCC 4.8.5 20150623 (Red Hat 4.8.5-11)] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import pyodbc
>>> pyodbc.connect(server="nz", database="TEST", dsn="NZSQL", user="admin", PWD="password", autocommit=False)
<pyodbc.Connection object at 0x7f66ef8566b0>

Install Netezza Linux client

First you need to download NPS Linux client from IBM Fix Central

Then, as root run following commands (accept all defaults):

mkdir NPS
cd NPS
tar xvfz ../nz-linuxclient-v7.2.1.4-P2.tar.gz
cd linux
cd ../linux64

Now, log in as nz user and add following lines to $HOME/.bashrc (modify credentials and server details accordingly: NZ_USER, NZ_PASSWORD and NZ_HOST):
export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:/usr/local/nz/lib64
export PATH=$PATH:/usr/local/nz/bin
export ODBCINI=$HOME/.odbc.ini

To make above changes effective without logging out and in, you can instead run command: . ./.bashrc

Now you should be able to use nzsql:

[nz@nzlinux ~]$ nzsql
Welcome to nzsql, the IBM Netezza SQL interactive terminal.
Type:  \h for help with SQL commands
       \? for help on internal slash commands
       \g or terminate with semicolon to execute query
       \q to quit

Setup ODBC

Copy following two files, odbc.ini and odbcinst.ini to /etc as root:


As nz user create following symlinks:

ln -s /etc/odbcinst.ini .
ln -s /etc/odbc.ini .
ln -s /etc/odbc.ini .odbc.ini
ln -s /etc/odbcinst.ini .odbcinst.ini


If you have any questions, please connect with me.


The .odbc.ini and .odbcinst.ini issues seems to be fixed with newer Python versions, so creating symlinks to users home directory nor creating system files under /etc are not anymore required. Just using .odbc.ini and .odbcinst.ini in user’s home directory works now as it is supposed to work.