about thumper aka sun fire x4500

[Adam McDougall]

On 01/17/12 17:09, Jeremy Chadwick wrote:
> On Tue, Jan 17, 2012 at 06:59:08PM +0100, peter h wrote:
>> I have been beating on of these a few days, i have udes freebsd 9.0 and 8.2
>> Both fails when i engage>  10 disks, the system craches and messages :
>> "Hyper transport sync flood" will get into the BIOS errorlog ( but nothing will
>> come to syslog since reboot is immediate)
>>
>> Using a zfs radz of 25 disks and typing "zpool scrub" will bring the system down in seconds.
>>
>> Anyone using a x4500 that can comfirm that it works ? Or is this box broken ?
>

I've seen what is probably the same base issue but on multiple x4100m2 
systems running FreeBSD 7 or 8 a few years ago.  For me the instant 
reboot and HT sync flood error happened when I fetched a ~200mb file via 
HTTP using an onboard intel nic and wrote it out to a simple zfs mirror 
on 2 disks.  I may have tried the nvidia ethernet ports as an 
alternative but that driver had its own issues at the time.  This was 
never a problem with FFS instead of ZFS.  I could repeat it fairly 
easily by running fetch in a loop (can't remember if writing the output 
to disk was necessary to trigger it).  The workaround I found that 
worked for me was to buy a cheap intel PCIE nic and use that instead of 
the onboard ports.  If a zpool scrub triggers it for you, I doubt my 
workaround will help but I wanted to relate my experience.

> Given this above diagram, I'm sure you can figure out how "flooding"
> might occur.  :-)  I'm not sure what "sync flood" means (vs. I/O
> flooding).

As I understand it, a sync flood is a purposeful reaction to an error 
condition as somewhat of a last ditch effort to regain control over the 
system (which ends up rebooting).  I'm pulling this out of my memory 
from a few years ago.