This is the spec of the server:-

Dell PowerEdge T710
2x 6 core Intel Xeon Processors
192GB RAM
8x 1TB SAS drives configured as RAID 5
Headless Ubuntu Server 18.04 LTS

The question is, after I powered on the server using the iDRAC interface, then after the system completely booted and the OS initialized, I can use the iDRAC virtual console to access everything just as if I'm using a KVM, in fact, I can also use the virtual console to power on, power off, and reboot the server and through the virtual console I can see the full POST procedures just as if I was looking at a monitor connected to the server, but, how is it that SSH access via PuTTY, is a lot faster than using the virtual console?

When I work through the virtual console (virtual KVM), everything is slow, directory listings scroll up slow as a snail, I enter commands and the results don't show up for at least 30s, but when I use SSH through PuTTY, it's 100x faster.

The server is in a climate controlled room, and admin access is only from within the LAN, with only the one workstation having access.

Could this be a Linux issue?

KVM is a virtualization layer, isn't it? So your path is via Nat, through the virtualization layer; and if you're using ssh, that's another overhead, not to mention another OS.

ssh --> putty is virtually straight out, so I would expect that to be maybe 2-3x faster, but in a simple console dialogue, you'd hardly notice a few milliseconds.

So I think you have a serious issue with your KVM config, or your nice numbers. No doubt you have good reasons for your linux on linux setup and I won't pry. I would start by getting some task of a few seconds going (copy a large file, make an iso) and try it a number of ways: Locally on your system; Locally on the 'linux on linux' system; process & transfer directly; process & transfer via ssh. Run top while you're at this and look for differences. Look for the bottlenecks. See that nothing is working with stupid numbers.

The virtual KVM is an addon module that plugs into the mobo, and has it's own dedicated LAN port, which when configured can only allow access through the LAN from only one source on the LAN, and the workstation I assigned for this is the one in my office.

I'm not sure what you mean by 'Linux on Linux setup'. Without the OS, and even without any HD's, by using iDRAC (integrated Dell Remote Access Controller), I can have access to every aspect of the server through a virtual console (virtual KVM), from setting up the 4 integrated LAN ports, to actually configuring the BIOS setup, and even as far as configuring the PERC, (PowerEdge Raid Controller), to even setting up power monitoring, etc etc all done remotely on the LAN, through the iDRAC interface, and even the iDRAC virtual console is very slow, because when I enter the console, and click on 'Power On', the console first shows 'No Connection', then it springs into like showing the server boot process, just as if I manually powered on a desktop machine and watched the boot process on a monitor, but when everything has been loaded and the command prompt appears on the virtual console, then I login and everything then starts slowing way down, I would describe it like using a terminal program on a dial up 54K modem, type something that wait for the echoed text to get back to the console, but if I exited the console, and started an SSH session using PuTTY, login to the OS, everything is about 10X faster than using the virtual console.

Along time a go, I used to have access to a dedicated server in a remote data center, and for me to install an OS, I used a KVM, which compared to the virtual console I use now completely on my LAN, the KVM I used on the data center machine is a damn site faster, and that was on the WAN.

Oh and I forgot to mention, my LAN is all gigabit, and I did a file transfer test, using command line FTP, first using the virtual console, it took 1h15m to transfer a 1.2GB ISO file, but using SSH via PuTTY only took, 3 minutes.

In this case KVM is Keyboard/Video/Mouse not the virtualization technology.

How responsive is the display in the BIOS/UEFI UI?

You could try disabling the frame buffer. The various ways to do it, I'm not sure what works for OpenSuSE, but something along the lines of adding 'nomodeset' to the grub command line.

While I have the console open, and click on 'Power On', and during POST, it does show. at the top right corner, a menu, so I press F2 to enter BIOS setup, and this is very quick, as is when I press CTRL-E to enter the iDRAC remote setup, or pressing CTRL-R for configuring PERC (PowerEdge Raid Controller), it's when the bootup sequence has completed and the system is loading the OS (ie Ubuntu server), that is when the console slows down, unlike Windoze, headless Linux echoes it's loading process to the screen, and it's this echoing during OS loading that is lagging, then once the OS has been loaded and the command prompt appears, the lagging is still there, but if I were to use SSH via PuTTY, and login through that, it's fast, but as SSH is under OS control, I can't use SSH as I would the virtual console, I can only use SSH once the OS has been fully loaded.

Here's one example of the lagging.

First using the virtual console, I power on the server, then wait until the OS has been fully loaded and the command prompt appears.
I log in, then I see the user prompt $>

I then issue 'sudo ls -R / -l' using sudo allows the listing command to show system directories too.
this will show a list of everything on the server, now, it's at this point that the listing 'crawls' up the screen, and I'm able to read at least 5 lines before it scrolls again.

I stop the listing using 'CTRL-C', then logout of the OS and close the virtual console.

Now, I start PuTTY in windoze, and connect via SSH, the login prompt appears to which I login, then I issue the same command 'ls -R / -l', and this time the response is like lightning, the listing scrolls up the screen faster than I can read it.

Here's 2 links to video screenshots I took, 1st the Virtual Console, then SSH, at first it says there's 8.0GB RAM, but there isn't, all banks are loaded, but for some reason, memory size is being mis-reported.

As can be seen the screen video for the virtual console, shows access is very slow, but the SSH one is fast.

Virtual Console:- https://www.dropbox.com/s/v54kwig1yb...nsole.mp4?dl=0

SSH PuTTY:- https://www.dropbox.com/s/b773v45uag...PuTTY.mp4?dl=0

Yeah... try disabling the frame buffer.