Display issue with KVM

PS/2 - USB - LCD Consoles - Remote Management
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mattw
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by mattw » Fri Jan 31, 2014 4:44 pm
We have just set up a KVM Console Pro with the 16 port KVM module.

We've connected up several of our servers and have run into an issue.

On the Servers running windows everything works very well, we get a clear picture and the keyboard and mouse are responsive.
However with the linux hosts we get a lot of distortion on the screen.

This makes the KVM virtually unusable on the Linux hosts and is very irritating.

We've tried rebooting the affected machines and using the autoconfigure button on the display to no avail.
A seperate LCD connected via VGA works fine and the cables don't seem to be at fault.

Any ideas? If this can't be resolved we might as well return the unit.
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Last edited by mattw on Fri Jan 31, 2014 4:48 pm, edited 1 time in total.

 

LINDY Shippers
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by LINDY Shippers » Mon Feb 03, 2014 2:28 pm
Hi,

We've never seen this issue with Linux (or even Windows)

What resolution is the console set at?

If you change the port on the KVM so the linux machine is on another, do you still get the same problem?

Chris

 

mattw
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by mattw » Mon Feb 03, 2014 2:31 pm
Resolution is 1280 x 1024

I've tried various ports on the KVM and all the Linux servers have the same issue. However, the windows servers seem fine.

I thought that it might be a framebuffer issue, however one of the windows servers uses the same hardware as the linux servers.

Is it possible that the KVM is not passing the console resolution back to the server?

 

LINDY Shippers
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by LINDY Shippers » Mon Feb 03, 2014 2:43 pm
On the linux machine do you get corruption when it boots in the BIOS?

Are you able to change the console resolution for testing purposes?

What type of cables are you using, with any adapters?

Chris

 

mattw
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by mattw » Mon Feb 03, 2014 2:45 pm
The console shows the BIOS perfectly.

I doubt I can change the resolution as the Linux servers just run TTY's without X11 installed. I might be able to specify a framebuffer resolution though.

We're using Part No. 33531 cables.

 

mattw
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by mattw » Mon Feb 03, 2014 5:06 pm
I've now done some more thorough tests.

There seem to be 3 display output qualities. Perfect, Grainy and Completely Distorted depending on stages of boot.
As the Linux machines don't negociate with the monitor once they have booted up, they are always 100% Distorted although powering off the KVM & Console at the mains and then powering it on again after 5 minues results in about 3 seconds with a clear picture.
Once the KVM is on the picture quality gradually gets worse over the course of about 30seconds, after which it's virtually impossible to make out anything on the screen.

Switching to a different windows host results in a clear picture but going back to a Linux host/ POST screen results in instant distortion.

Boot stages test results with different machines:

Windows machine (IBM 1u server):
POST Screen: Badly Distorted. Barely visable
IBM BIOS/UEFI Splash: Perfect
Windows Boot Screen: Grainy
Windows Login Screen + Desktop: Perfect

Linux machine (Fujitsu 1u server)
POST Screen: Badly Distorted. barely Visible
BIOS: Perfect
Boot Post Screen (PXE Boot): Distorted
Grub: Grainy
(Tried two options from here)
Boot as standard: 720x400 TTY V: 70.3Hz : Completely Distorted
Boot with modeline 775 (1280x1024_60.2Hz): Grainy for boot , completely distorted once I reach a TTY

I'm guessing that the machines output at ~70Hz unless a specific screen (BIOS, windows login etc...) sets it differently.

We also have a KVM Console Basic. I've tried it with the machines one by one (we have 4 windows hosts, 9 linux hosts) and it seems to have no problems with any of them.
Seperate Monitors also seem to have no issues.

Could this be a fault with either the KVM or the console?

Thanks,

Matt
Last edited by mattw on Mon Feb 03, 2014 5:12 pm, edited 1 time in total.

 

LINDY Shippers
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by LINDY Shippers » Tue Feb 04, 2014 10:02 am
From the extensive testing you have done above I'd suggest the KVM unit has a fault.

Please could you return the unit to us for testing - http://www.lindy.co.uk/return-product-i374

Chris

 

mattw
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by mattw » Tue Feb 04, 2014 2:49 pm
I removed the KVM switch from the rack and as we had the kvm cable that came with the console I have tested the KVM console directly with the servers and the issue is exactly the same. From this it is now my opinion that it is the KVM Console that is at fault.

 

LINDY Shippers
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by LINDY Shippers » Tue Feb 04, 2014 3:55 pm
Sorry when I said "KVM unit" I should have said Console+KVM

However since it looks like the console only then it would be fine to return just that part.

Chris

 

mattw
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by mattw » Wed Feb 26, 2014 4:50 pm
Just to update the thread, the unit was deemed faulty and a replacement was provided.

The replacement is working perfectly and after some fairly thorough testing we have no encountered any more issues.

Thanks,

Matt
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