[CLOUDSTACK-10151] Creating VMs from a snapshot delta fails

• Type: Bug
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: 4.9.0
• Component/s: Secondary Storage, Snapshot, Template, XenServer
• Security Level: Public (Anyone can view this level - this is the default.)
• Environment: xenserver 7.0, cloudstack 4.9.3, centos 7, nfs
• Assignee: Unassigned
• Reporter: Vincent Vuong
• Created: 21/Nov/17 07:28
• Updated: 21/Nov/17 07:28

Description

There seems to be a bug when trying to create a template from a delta snapshot. The template is created successfully but the VM created from the template encounter the following error when trying to boot.

2017-11-20 19:47:54,066 WARN [c.c.h.x.r.CitrixResourceBase] (DirectAgent-492:ctx-74102b57) (logid:1e8dbbd6) Task failed! Task record: uuid: 3af417f7-106b-af23-1422-e2580d60875b
nameLabel: Async.VM.start_on
nameDescription:
allowedOperations: []
currentOperations: {}
created: Mon Nov 20 19:47:52 PST 2017
finished: Mon Nov 20 19:47:53 PST 2017
status: failure
residentOn: com.xensource.xenapi.Host@e9e4116e
progress: 1.0
type: <none/>
result:
errorInfo: [BOOTLOADER_FAILED, OpaqueRef:fa4d6123-a5ea-1f2e-3f9a-ae10d722c84c, Bootable disk has no valid filesystem
]
otherConfig: {}
subtaskOf: com.xensource.xenapi.Task@aaf13f6f
subtasks: []

2017-11-20 19:47:54,082 WARN [c.c.h.x.r.CitrixResourceBase] (DirectAgent-492:ctx-74102b57) (logid:1e8dbbd6) Unable to start VM(i-2-333-VM) on host(a61acf06-3c69-413f-b944-315f05c07ffe) due to Task failed! Task record: uuid: 3af417f7-106b-af23-1422-e2580d60875b
nameLabel: Async.VM.start_on
nameDescription:
allowedOperations: []
currentOperations: {}
created: Mon Nov 20 19:47:52 PST 2017
finished: Mon Nov 20 19:47:53 PST 2017
status: failure
residentOn: com.xensource.xenapi.Host@e9e4116e
progress: 1.0
type: <none/>
result:
errorInfo: [BOOTLOADER_FAILED, OpaqueRef:fa4d6123-a5ea-1f2e-3f9a-ae10d722c84c, Bootable disk has no valid filesystem
]
otherConfig: {}
subtaskOf: com.xensource.xenapi.Task@aaf13f6f
subtasks: []

The VHD chain on the primary storage looks correct with parent and child existing.

vhd=96297418-afa2-4dcb-84a4-f8ed7b37535e.vhd capacity=21474836480 size=1758786048 hidden=1 parent=none
vhd=f2ec7a29-4ff6-4a88-a759-9337e120901c.vhd capacity=21474836480 size=46592 hidden=0 parent=96297418-afa2-4dcb-84a4-f8ed7b37535e.vhd
vhd=f02924ea-a969-43c9-a17e-759b9cb56920.vhd capacity=21474836480 size=117715456 hidden=1 parent=96297418-afa2-4dcb-84a4-f8ed7b37535e.vhd
vhd=69a5e584-886b-4f0b-b24e-5cdfa9915907.vhd capacity=21474836480 size=46592 hidden=0 parent=f02924ea-a969-43c9-a17e-759b9cb56920.vhd
vhd=e945d3d3-dc1e-45e6-9697-14f292cf402d.vhd capacity=21474836480 size=39969280 hidden=1 parent=f02924ea-a969-43c9-a17e-759b9cb56920.vhd
vhd=715a965a-a66c-437d-a68c-1ab794ec6fd1.vhd capacity=21474836480 size=46592 hidden=0 parent=e945d3d3-dc1e-45e6-9697-14f292cf402d.vhd
vhd=e2d52d83-5c36-4824-89ea-33123a154b78.vhd capacity=21474836480 size=46443008 hidden=0 parent=e945d3d3-dc1e-45e6-9697-14f292cf402d.vhd

The VHD chain on the secondary storage are both parents even with the second snapshot is a delta snapshot. Cloudstack 4.2 VHD chain on the secondary storage had both parent and child.

vhd=0ada1766-f42e-41a0-bc16-7c38f4b259e3.vhd capacity=21474836480 size=39965184 hidden=0 parent=none
vhd=bf602629-8851-4492-9c95-d4c99ab36aa5.vhd capacity=21474836480 size=1765089792 hidden=0 parent=none

Steps to recreate the problem are:

1) Create VM ISO or any working templates
2) Take snapshots number 1
3) Create test file in VM
4) Take snapshots number 2
5) Create template from snapshots number 2
6) Create VM from template

VM creation will fail. The install is a fresh CS 4.9.3 and Xenserver 7.0 with latest patches. CS 4.9.3 and Xenserver 6.5 also produced the same error.

Workaround is to disable delta snapshots by setting snapshot.delta.max to 1.