Diagnosing a random reboot

[diskdiddler]

Hi all,

I don't beleive FreeNAS ever reboots itself without permission, right?
I've not configured scripts to do so - but when starting a PBI on the system just now, the machine rebooted itself.
Which log file should I be looking at to find the cause of this? Not ideal.

EDIT
HP Microserver N40L, 8GB ram, FreeNAS 9.2.1.6 with 4 plugins (Couchpotato, Sickbeard, Crashplan, SabNZBD)

 

[diskdiddler]

BTW, Cyberjock - before you even say it, if we can prove from this reboot, it's 100% a memory issue, yes, I'll go and order 16GB of ECC, but I ain't doing it until I know for sure.
(and I still feel like, if a machine IS lacking in ram, it should have warnings / errors/ something rather than just rebooting)

I'm hoping it was infact a software issue - I don't like the idea of my volume being at risk due to reboots.
P.S Hardware stable under Windows over a year.

 

[cyberjock]

No, FreeNAS never does a reboot from a running state, with two exceptions:

1. A kernel panic (BSOD for Windows users)
2. You are doing a FreeNAS upgrade in which case it does 2 reboots.

If the machine were lacking RAM you'll get a kernel panic right before the reboot. Not looking at the screen? Too bad, you missed the error.

So if you say you didn't tell the box to reboot and it did, then I'd say it's nearly 100% certainty that you had a kernel panic. ;)

You also failed to list server specs, version, etc as required in the forum rules. So please add that stuff for future readers.

 

[diskdiddler]

It occurred exactly when I started a PBI, so I figure that may have been related somehow.
Is there any log I could trawl regardless to check? or is it likely to have never made it to disk?
Why would a kernel panic occur on a machine without faulty hardware, why would it not instead slow down for page file or something?

 

[Yatti420]

Well if your syslog is on your pool you could look there for it.. I believe it's in a hidden folder now.. If you checked to make sure your ram isn't bad before install of hardware could just be a random reboot but I've never seen a FreeNAS box do this without hardware issues..

 

[cyberjock]

Why would a kernel panic occur on a machine without faulty hardware, why would it not instead slow down for page file or something?

Because kernel space cannot be swapped. So if you run out of kernel space (which means you run out of RAM) = instant kill for the server.

See why RAM is so important yet? ;)

 

[diskdiddler]

Because kernel space cannot be swapped. So if you run out of kernel space (which means you run out of RAM) = instant kill for the server.

See why RAM is so important yet? ;)

So why is the kernel space exceeding 8gb of ram? Surely the critical aspect of the kernel doesn't exceed 8gb of ram generally? Does the memory allocated to mapping the storage pool in memory, become "part of" the kernel space during OS operation? - if that was the case, I guess I can see why a larger pool would literally make the machine crash.

As for the physical hardware, it's definitely fine, I've ran memtest on this thing for a week, it was originally going to be a VM server for a smallbusiness.

 

[cyberjock]

It's not exceeding 8GB of RAM. You have something like 1-1.5GB of RAM for ramdrives since FreeNAS runs from ram disks, then you have other applications and services, then what's left for the kernel space. ZFS runs in kernel space, hence you need enough RAM to keep it happy.

 

[diskdiddler]

So what / where is the log I should be examining to investigate this anyhow? Any suggestions?