FreeNAS system tortured for 2 years finally...

[fluflux]

... upgraded to 9.3 and it still rocks! :).

You guys spend so much time to solve problems, I first want to mention that FreeNAS is working absolutely perfect for me.

Over those 2 years, I have done the following things, without FreeNAS giving a hitch:

• "Cheated" by setting up a 7 disk raidz2 pool having only 6 disks, using it a few months until I had a controller for the 7th :).
• Twice migrated a 7 disk raidz2 pool to new disks (upgrading it disk by disk), right now I'm at 7x6TB raidz2
• Migrated from an encrypted disk set to a non encrypted disk-set via the "risky" way (disk by disk, manually offlining and then replacing with an unencrypted one)
• Tested the reliability by from time to time randomly detaching a drive, and then resilvering it without issue.

So, all very happy about this. Now with FreeNAS 9.3 one of my big wishes came true, having virtualisation out of the box. This is really awesome. Given my machine has 24GB of RAM, I have some to spare for a VM or two, and I've been able to set up a VM to sync dropbox to a samba share as well, so now I have dropbox on my NAS :).

Two questions I have that I hope somebody can inform me on:
1) Is there a 'reliability' risk in using my FreeNAS box as a VM Host? Can people with knowledge of the FreeNAS/FreeBSD & virtualbox architecture comment on this? For example, does the virtual machine feature have some kind of kernel module running inside the FreeNAS kernel that could bring the machine down in case that kernel module has a bug? Could it have impact on the storage subsystem or not at all? What's the stability and reliability impact?
2) I'm using many snapshots. I have about 120 active, which isn't that much, but there's a huge amount of rotation. Some are taken every hour, kept 24 hours, some every day, kept a week, ... Is that kind of usage going to affect the speed of ZFS in any way?

Thanks!

 

[Bidule0hm]

2) No problem at all. Snapshots are very light ;)

 

[cyberjock]

1) The kernel module loads for everyone, even those that don't use Virtualbox.

And problems will only develop if if you try to overload the system's capabilities. I wouldn't recommend RAIDZ2 for VMs. You'll find you run out of iops really fast with just one VM running.

 

[fluflux]

Ok, thanks for the replies. I'm considering adding an SSD to the server and configure it as a separate zpool to be used for VMs only. That pool would then get backed up to the main pool once a day.

 

[Robert Trevellyan]

1) does the virtual machine feature have some kind of kernel module running inside the FreeNAS kernel that could bring the machine down in case that kernel module has a bug? Could it have impact on the storage subsystem or not at all?

I recently had a VM lock up and peg its virtual CPU at 100%. Because my CPU has 4 hyper-threaded cores, that represented 12.5% CPU usage on the box, which is how I noticed it (in the Reporting tab). It had no obvious impact on the rest of the system, which is very lightly loaded. I killed the VM and restarted it, without any lasting effects. That's one of the reasons to use virtualization to begin with.

 

[fluflux]

........ and today, virtualbox crashed my FreeNAS box

Seems I was at least somewhat right regarding a stability risk ;). What happened was very simple. I had a virtualbox (ubuntu) instance running for a couple of days, and then I decided to stop it. Instead of shutting it down via phpvirtualbox, I tried to shut down the jail virtualbox was running in instead, via the FreeNAS GUI. Immediately (1 second) after I did that, my FreeNAS server rebooted. This probably would not have happened if I had shut down the virtualbox instance via phpvirtualbox first, and then stopped the jail, but that's not the point.

The point is that through it's kernel module, virtualbox crashed my entire freenas server! What cyberjock mentioned before, that the module runs for everybody, is hardly relevant. Besides maybe some minimal initialization, it will only execute (and exhibit any kernel crashing bugs it has) when you use it.

Conclusion for me? I'm not going to stop using virtualbox, way to useful for that (so thx cyberjock, as I think you created the first working version of it). It could crash my box maybe again (who knows), but I'm one of those guys with a "full backup of my backup" in my sleeve so I'll survive even the worst crash.

I looked at the log files but there was nothing useful to be found before the crash, just virtualbox shutting down and then crashing. If anybody is interested I can do more experiments on request.

 

[cyberjock]

Well, you'd make the first person I can think of that crashed their box as a result of Virtualbox....

 

[fluflux]

I see, my FreeNAS box decided to take revenge after all the risky things I did with it earlier :).
It remains a "guess" of course, as the reason I believe VirtualBox to be the culprit is the timing of the crash being within one second of shutting down a VBox jail with a running VBox instance.
Today I tried to reproduce the same scenario again, but this time there was no crash, the system kept going smoothly.