kernel-packages team mailing list archive

[Frederik Bosch <f.bosch@xxxxxxxxx>]

This problem started more than a year ago, I decided together with my
hoster to look at alternatives. Backup is the only thing that is causing
problems for us with HyperV. The problem is two fold. First, the read-
only state machines get into when generating the backup. Second, the
read/write spike we see during a backup.

While this topic is focussed on the backups, the latter (spikes) is more
and more causing problems. The more data getting on the disk, the higher
the spikes are. Http requests that usually take < 100 ms are causing
multiple seconds. More specifically, requests that involve write
operations tend to have these characteristics. The read-only already
made us reduce the amount of backups, because we want to decrease the
risk of downtime. Now, with this (new) problem, it is almost impossible
that a client does not suffer from a backup. That situation is wrong.

Since, it is so hard to debug (impossible for us to replicate behaviour
on a test machine) and it is hard to tell when the problem will be
solved, we decided, after a year, to look at alternatives. Nonetheless,
thanks for the help we got here. That is much appreciated.

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https://bugs.launchpad.net/bugs/1470250

Title:
  [Hyper-V] Ubuntu 14.04.2 LTS Generation 2 SCSI Errors on VSS Based
  Backups

Status in linux package in Ubuntu:
  In Progress
Status in linux source package in Trusty:
  In Progress
Status in linux source package in Utopic:
  In Progress
Status in linux source package in Vivid:
  In Progress
Status in linux source package in Wily:
  In Progress

Bug description:
  Customers have reported running various versions of Ubuntu 14.04.2 LTS
  on Generation 2 Hyper-V Hosts.    On a random Basis, the file system
  will be mounted Read-Only due to a "disk error" (which really isn't
  the case here).    As a result, they must reboot the Ubuntu guest to
  get the file system to mount RW again.

  The Error seen are the following:
  Apr 30 00:02:01 balticnetworkstraining kernel: [640153.968142] storvsc: Sense Key : Unit Attention [current] 
  Apr 30 00:02:01 balticnetworkstraining kernel: [640153.968145] storvsc: Add. Sense: Changed operating definition
  Apr 30 00:02:01 balticnetworkstraining kernel: [640153.968161] 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.
  Apr 30 01:23:26 balticnetworkstraining kernel: [645039.584164] hv_storvsc vmbus_0_4: cmd 0x2a scsi status 0x2 srb status 0x82
  Apr 30 01:23:26 balticnetworkstraining kernel: [645039.584178] hv_storvsc vmbus_0_4: stor pkt ffff88006eb6c700 autosense data valid - len 18
  Apr 30 01:23:26 balticnetworkstraining kernel: [645039.584180] storvsc: Sense Key : Unit Attention [current] 
  Apr 30 01:23:26 balticnetworkstraining kernel: [645039.584183] storvsc: Add. Sense: Changed operating definition
  Apr 30 01:23:26 balticnetworkstraining kernel: [645039.584198] 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.

  This relates to the VSS "Windows Server Backup" process that kicks off at midnight on the host and finishes an hour and half later.   
  Yes, we do have hv_vss_daemon and hv_kvp_daemon running for the correct kernel version we have.   We're currently running kernel version 3.13.0-49-generic #83 on one system and 3.16.0-34-generic #37 on the other. -- We see the same errors on both.
  As a result, we've been hesitant to drop any more ubuntu guests on our 2012R2 hyper-v system because of this.   We can stop the backup process and all is good, but we need nightly backups to image all of our VM's.   All the windows guests have no issues of course.   We also have some CentOS based guests running without issues from what we've seen.

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