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IDProjectCategoryView StatusLast Update
0014482CentOS-6kernelpublic2018-02-12 18:48
Status newResolutionopen 
PlatformHyper-V Generation 2 VMOSCentosOS VersionCentos 6.9
Product Version 
Target VersionFixed in Version 
Summary0014482: Centos 6.9 guest on Hyper-V Generation-2 virtual machine block devices initialization issue
DescriptionAll Centos 6.9 2.6.32-696 kernel series pause during boot for large intervals (tens of seconds) while initializing block devices when Centos 6.9 is used as a guest under Hyper-V Generation 2 Virtual Machines in Windows Server 2016 version 1607.
- The issue does not occur with 2.6.32-642 kernel series of Centos 6.8
- The issue does not occur with Generation-1 Hyper-V VMs and Centos 6.9
Steps To ReproduceInstall Centos 6.9 as Guest under Hyper-V as Generation-2 Virtual Machine in Windows Server 2016 version 1607.
Assigned RAM, Virtual CPU count does not affect the issue.
The tests were performed with one scsi contoller with a dynamic expanding 127 Gib virtual disk at position 0 and one cdrom at position 1 and with disabled secure boot.

The issue is also reproducible with Hyper-V Generation-2 VMs under windows 10 Professional version 1709.
Additional InformationWith the same VM configuration Centos 6.8 takes 7 seconds to boot, while Centos 6.9 takes 88 seconds to boot.

In order to get accurate timing for printk messages the rhgb quit is removed and printk.time=1 is added to kernel line at grub.conf

As it can be seen from the attached kernel log, the kernel pauses:
For 20 seconds at:
[ 0.694904] sr 0:0:0:1: Attached scsi CD-ROM sr0
[ 20.837103] dracut: Starting plymouth daemon

For 30 seconds at:
[ 20.865167] dracut: rd_NO_MD: removing MD RAID activation
[ 51.092274] dracut: Scanning devices sda3 for LVM logical volumes VolGroup/lv_swap VolGroup/lv_root

And finally for another 30 seconds at:
[ 53.465081] sr 0:0:0:1: Attached scsi generic sg1 type 5
[ 84.576559] EXT4-fs (sda2): mounted filesystem with ordered data mode. Opts:
Tagsboot, hyper-v, kernel




2018-02-12 14:01


logs.tar.gz (23,212 bytes)


2018-02-12 18:48

reporter   ~0031217

I removed the virtual scsi cdrom drive and all the pauses are gone. Now Centos 6.9 booted at 8 seconds.
I checked the Centos 6.8 kernel logs more thoroughly and there are a couple of the following messages:

storvsc: Sense Key : Not Ready [current]
storvsc: Add. Sense: Medium not present - tray closed
storvsc: Sense Key : Not Ready [current]
storvsc: Add. Sense: Medium not present - tray closed
storvsc: Sense Key : Not Ready [current]

and they not appear in Centos 6.9 kernel log.
For some reason the Centos 6.9 kernel cannot determine that the virtual scsi cdrom drive has no medium.

Issue History

Date Modified Username Field Change
2018-02-12 14:01 nkef New Issue
2018-02-12 14:01 nkef File Added: logs.tar.gz
2018-02-12 14:01 nkef Tag Attached: boot
2018-02-12 14:01 nkef Tag Attached: hyper-v
2018-02-12 14:08 nkef Tag Attached: kernel
2018-02-12 18:48 nkef Note Added: 0031217