2018-02-19 13:59 UTC

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IDProjectCategoryView StatusLast Update
0014482CentOS-6kernelpublic2018-02-12 18:48
Reporternkef 
PrioritynormalSeveritymajorReproducibilityalways
StatusnewResolutionopen 
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
Attached Files

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-Notes

~0031217

nkef (reporter)

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.
+Notes

-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
+Issue History