Resizing of volumes used as VMWare NFS datastores causes Linux VM issues

We had to perform a live volume resize of an NFS datastores VMWare uses on our Netapp. All of our Windows VMs were fine after the resize. However, some of our Linux VMs had issues.

Some Linux VMs just stopped responding. After restarting those VMs, I couldn't find anything in the logs indicative of an issue though.

I did find these kind of log messages on some of the VMs however:

May 29 14:56:02 rhel6-server-1314 kernel: INFO: task jbd2/dm-0-8:382 blocked for more than 120 seconds.
May 29 14:56:02 rhel6-server-1314 kernel: "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
May 29 14:56:02 rhel6-server-1314 kernel: jbd2/dm-0-8   D 0000000000000000     0   382      2 0x00000000
May 29 14:56:02 rhel6-server-1314 kernel: ffff880037ce9c20 0000000000000046 ffff880037ce9be0 ffffffffa00041fc
May 29 14:56:02 rhel6-server-1314 kernel: ffff880037ce9b90 ffffffff81012b59 ffff880037ce9bd0 ffffffff8109b809
May 29 14:56:02 rhel6-server-1314 kernel: ffff880037ce1af8 ffff880037ce9fd8 000000000000f4e8 ffff880037ce1af8
May 29 14:56:02 rhel6-server-1314 kernel: Call Trace:
May 29 14:56:02 rhel6-server-1314 kernel: [<ffffffffa00041fc>] ? dm_table_unplug_all+0x5c/0x100 [dm_mod]
...             rhel6-server-1314
May 29 14:56:02 rhel6-server-1314 kernel: [<ffffffff8100c140>] ? child_rip+0x0/0x20
May 29 14:56:02 rhel6-server-1314 kernel: INFO: task master:1674 blocked for more than 120 seconds.
May 29 14:56:02 rhel6-server-1314 kernel: "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
May 29 14:56:02 rhel6-server-1314 kernel: master        D 0000000000000000     0  1674      1 0x00000080
May 29 14:56:02 rhel6-server-1314 kernel: ffff88003d669958 0000000000000086 ffff88003d669918 ffffffffa00041fc
May 29 14:56:02 rhel6-server-1314 kernel: 0000000000000000 ffff880002216028 ffff880002215fc0 ffff88003fac2b78
May 29 14:56:02 rhel6-server-1314 kernel: ffff88003fac30f8 ffff88003d669fd8 000000000000f4e8 ffff88003fac30f8
May 29 14:56:02 rhel6-server-1314 kernel: Call Trace:
May 29 14:56:02 rhel6-server-1314 kernel: [<ffffffffa00041fc>] ? dm_table_unplug_all+0x5c/0x100 [dm_mod]
...             rhel6-server-1314
May 29 14:56:02 rhel6-server-1314 kernel: [<ffffffff8100b0f2>] system_call_fastpath+0x16/0x1b
May 29 14:56:02 rhel6-server-1314 kernel: INFO: task pickup:6197 blocked for more than 120 seconds.
May 29 14:56:02 rhel6-server-1314 kernel: "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
May 29 14:56:02 rhel6-server-1314 kernel: pickup        D 0000000000000000     0  6197   1674 0x00000080
May 29 14:56:02 rhel6-server-1314 kernel: ffff88003da95968 0000000000000086 ffff88003da95928 ffffffffa00041fc
May 29 14:56:02 rhel6-server-1314 kernel: ffff88003da95938 ffff8800022128a0 ffff88003da95908 ffffffff81127ed0
May 29 14:56:02 rhel6-server-1314 kernel: ffff88003d90da78 ffff88003da95fd8 000000000000f4e8 ffff88003d90da78
May 29 14:56:02 rhel6-server-1314 kernel: Call Trace:
May 29 14:56:02 rhel6-server-1314 kernel: [<ffffffffa00041fc>] ? dm_table_unplug_all+0x5c/0x100 [dm_mod]
...             rhel6-server-1314
May 29 14:56:02 rhel6-server-1314 kernel: [<ffffffff8100b0f2>] system_call_fastpath+0x16/0x1b
May 29 14:56:02 rhel6-server-1314 kernel: mptscsih: ioc0: attempting task abort! (sc=ffff880037bfd280)
May 29 14:56:02 rhel6-server-1314 kernel: sd 2:0:0:0: [sda] CDB: Write(10): 2a 00 03 14 e8 d0 00 00 18 00
May 29 14:56:02 rhel6-server-1314 kernel: mptscsih: ioc0: WARNING - Issuing Reset from mptscsih_IssueTaskMgmt!! doorbell=0x24000000
May 29 14:56:02 rhel6-server-1314 kernel: mptscsih: ioc0: task abort: SUCCESS (rv=2002) (sc=ffff880037bfd280)
May 29 14:56:02 rhel6-server-1314 kernel: scsi target2:0:0: Beginning Domain Validation
May 29 14:56:02 rhel6-server-1314 kernel: scsi target2:0:0: Domain Validation skipping write tests
May 29 14:56:02 rhel6-server-1314 kernel: scsi target2:0:0: Ending Domain Validation
May 29 14:56:02 rhel6-server-1314 kernel: scsi target2:0:0: FAST-40 WIDE SCSI 80.0 MB/s ST (25 ns, offset 127)

My questions:

1. Does anyone know what is causing this?
2. If not, where else should we look for clues?
3. Finally, does anyone know how to mitigate this next time we have to do a volume resize?

Solution 1:

I think, it was just an I/O timeout.

I had such issues with Linux VMs on remote NFS datastore. NFS was just too slow, and some of our Linux VMs switched their disks into read-only mode (and therefore stopped responding). Probably, during resize your NFS datastore was overloaded and this caused issues. Do Linux VMs work fine after reboot?

To avoid such issues, and slightly improve I/O performance for Linux guests, you could try to switch I/O scheduler to "noop" or "deadline" for all guests:

http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=2011861

In my case, we had such timeout issues approximately once a week on the most loaded Linux guests, even with "scheduler fix". To solve it, we switched from NFS to iSCSI (you could also try to optimise your NFS settings like "rsize", "wsize", MTU and so on, but it was still not enough in my case) and tried to reduce I/O operation on guests whenever it was possible.

Solution 2:

If this is a NetApp (or any other NFS server), be sure that the NFS best-practices for the ESXi host configurations are in place.

For NFS deployments, I always make some adjustments to NFS heartbeat and timeout settings. That may apply in your case. Check with your storage engineer to see what the specific recommendations for your unit are.