I have Ubuntu Server 14.04.1 LTS running in a Hyper-V virtual machine on a Windows 2012 R2 host.
After running for some time, the Ubuntu server seems to freeze up (at least partially). A website it's hosting under nginx stops working. I can connect via Putty and enter my username and password, but then the session immediately hangs:
The same thing happens when I try to log in from the console (making it difficult to check logs / troubleshoot). However I do notice output like this sitting in the console window:
If there is a local or remote console session that is already logged in, I can still interact with it. However any attempt to write to the disk freezes the session.
I believe the issue may be related to the disk I/O stack:
[16209.927138] hv_storvsc vmbus_0_13: cmd 0x35 scsi status 0x2 srb status 0x82 [16209.927142] hv_storvsc vmbus_0_13: stor pkt ffff88003b203100 autosense data valid - len 18 [16209.927144] storvsc: Sense Key : Unit Attention [current] [16209.927146] storvsc: Add. Sense: Changed operating definition [16209.927151] sd 0:0:0:0: Warning! Received an indication that the operating parameters on this target have changed. The Linux SCSI layer does not automatically adjust these parameters. [45841.680551] INFO: task rs:main Q:Reg:882 blocked for more than 120 seconds. [45841.680580] Not tainted 3.13.0-32-generic #57-Ubuntu [45841.680596] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
The install is fairly fresh and default settings were accepted for pretty much everything. The VM is using Hyper-V's "generation 2" guest architecture, with secure boot disabled.
The server still responds to pings. Also note we saw the freezing behavior before nginx was installed.
I don't think it's a resource issue. The VM has 1GB of RAM and plenty of disk space. Here's what things look like before it freezes:
System information as of Sun Aug 3 16:03:30 EDT 2014 System load: 0.08 Processes: 231 Usage of /: 3.6% of 96.59GB Users logged in: 1 Memory usage: 29% IP address for eth0: 172.22.0.26 Swap usage: 0%
I'm looking for:
Tips on how to efficiently troubleshoot this
Instructions on how to turn off any sort of disk-related features (e.g. power saving) that came out of the box in my Ubuntu install.
A recommendation on where to find a Linux + Hyper-V genius we can hire remotely to help sort this out (and maybe other occasional Linux work)