[Gllug] Hardware problems / good replacements

Phil Reynolds phil-gllug at tinsleyviaduct.com
Mon Feb 27 14:39:11 UTC 2012

On 11/02/12 19:40, James Courtier-Dutton wrote:
> On 10 February 2012 22:40, Phil Reynolds <phil-gllug at tinsleyviaduct.com> wrote:
>> Hmmm... how could I check for a system timer problem?
> Start with a PC that is keeping accurate time that you trust, using ntpd.
> One way to check the timer is to just type "date" at the command line
> in the VM and compare it the other trusted machine. Note the
> difference, to the nearest second or two.
> Then, wait about 10 mins and try it again, and see how far out it is that time.
> If the difference is the same both times, you don't have a timer
> problem, if the time is out, then there is your problem.
> On problem machines, I saw the time drifting out by more than 10
> seconds over a 10 minute period, so it is easy to spot.
> If the time is your problem, you need to look at virtualised
> clock-source drivers for inside the VM.

Well, I finally finished the task of bringing my VMs up to date. I've
also now tried this test. Only in NetBSD did it fail.

Guest system		Time drift	Messages		Notes
============		==========	========		=====

FreeBSD 9.0		0s in 10 min	None			None
NetBSD 5.1_STABLE	102s in 10 min	None			None
OpenBSD 5.0-stable	1s in 10 min	None			Note 1
Debian kFreeBSD 6.0	1s in 13 min	Message 1 below		None
Debian Linux wheezy	0s in 10 min	None			None
Reactos 0.3.14		0s in 10 min	N/A			None
Windows 7		2s in 2h10m	N/A			None

Message 1:
ad0: TIMEOUT - WRITE_DMA retrying (1 retry left) LBA=... (number varies)

(FreeBSD 8.x used to do the same)

Note 1: OpenBSD result above is with acpihpet* disabled as per the
suggestion at http://tinyurl.com/7ov4ezw - although with acpihpet*
enabled, the result is the same, so obviously not significant in this
case. As it defaults to enabled, I will leave it so.

These are all still on the qemu-kvm that came with Debian Linux
squeeze... I have not yet tried the backports, but I intend to do so.

Phil Reynolds
mail: phil-gllug at tinsleyviaduct.com
Gllug mailing list  -  Gllug at gllug.org.uk

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