Loading

×Sorry to interrupt
CSS Error

Refresh

Cookie Preference Center

General Information on cookies

When you visit our website, we use cookies to ensure that we give you the best experience. This information does not usually directly identify you, but it can give you a more personalized web experience. Because we respect your right to privacy, you can choose not to allow some types of cookies by clicking on the different category headings to find out more and change your settings. However, blocking some types of cookies may impact your experience on the site and the services we are able to offer. Further information can be found in our

Cookie Policy.

Strictly Necessary

Strictly Necessary

Always Active

Strictly Necessary

Strictly necessary cookies are always enabled since they are essential for our website to function. They enable core functionality such as security, network management, and website accessibility. You can set your browser to block or alert you about these cookies, but this may affect how the website functions. For more information please visit www.aboutcookies.org or www.allaboutcookies.org.

Cookie Details‎

Performance

Performance

Performance

Performance cookies are used to analyze the user experience to improve our website by collecting and reporting information on how you use it. They allow us to know which pages are the most and least popular, see how visitors move around the site, optimize our website and make it easier to navigate.

Cookie Details‎

Please confirm your settings by refreshing the page.

Functional

Functional

Functional

Functional cookies help us keep track of your past browsing choices so we can improve usability and customize your experience. These cookies enable the website to remember your preferred settings, language preferences, location and other customizable elements such as font or text size. If you do not allow these cookies, then some or all of these services may not function properly.

Cookie Details‎

Advertising

Advertising

Advertising

Advertising cookies are used to send you relevant advertising and promotional information. They may be set through our site by third parties to build a profile of your interests and show you relevant advertisements on other sites. These cookies do not directly store personal information, but their function is based on uniquely identifying your browser and internet device.

Cookie Details‎

Advertising Cookies

Consent Leg.Interest

Select All Vendors

Select All Vendors

Select All Hosts

Select All

Clear Filters

Information storage and access

Apply

Confirm My Choices Reject All Allow All

Skip to main content

Products and Accounts

Support

Knowledge

Communities

Success

Learning

My Subscriptions

Loading

Knowledge Base

Snapshot removal stops a virtual machine for long time (1002836)

Last Updated: 8/20/2021Categories: InformationalTotal Views: 381751Language:
Chinese (Simplified)Portuguese (European)JapaneseSpanishEnglish

49 like this article

Subscribe to get an email
newsletter with new updates

49 people found this helpful Please provide article feedback:

Learn how VMware Skyline Advisor and Skyline Health Diagnostics work together to provide proactive intelligence and self-service log analysis.

Use Skyline Advisor to avoid issues before they occur across VCF, vSphere, vSAN, NSX, vROps & Horizon. Skyline Findings are based on top KBs, VMSAs/CVEs and design best practices.

Use Skyline Health Diagnostics to root cause vSphere & vSAN logs when an issue occurs. Skyline Health Diagnostic Findings are based on top KBs and VMSA/CVEs. You can use the Skyline Health Diagnostics tool in online or offline mode.

If you require additional help from technical support, please use Skyline Advisor to initiate a Log Assist to reduce time to upload logs. TSEs can also initiate logs to reduce effort.

Details

When a snapshot removal (consolidation) is in progress, you cannot perform other VM tasks, such as power operations, or vMotion migration, in the virtual machine. You must remove the snapshot without any interruption to ensure data integrity. Based on the amount of snapshot delta to be committed, the amount of time varies.

This article outlines the actions taking place against the virtual machines snapshots.

Note: Verify if the Virtual Machine is in responsive state by performing a ping test or trying to access the VM through RDP.

Solution

For live consolidations, virtual machine activity (specifically disk writes) during this time must also be committed. This delta information is kept through svm mirror device that is responsible for copying the data, committed at the end of the snapshot removal.

For busy virtual machines, the volume of activity may consume system resources for longer than a usual amount of time, resulting in a larger Consolidate Helper snapshot delta.

For example, a virtual machine with one virtual disk (disk.vmdk) and one snapshot, will have these files:

disk.vmdk with extent disk-flat.vmdk

disk-000001.vmdk with extent disk-000001-delta.vmdk

If you choose to remove or consolidate the snapshot:

An additional snapshot delta is created, the Consolidate Helper:

disk.vmdk with extent disk-flat.vmdk

disk-000001.vmdk with extent disk-000001-delta.vmdk

disk-000002.vmdk with extent disk-000002-delta.vmdk. The virtual machine is no longer writing to the above two files; all current writes while the snapshot removal is in progress are committed to the disk-000002-delta.vmdk extent file via disk-000002.vmdk.

The VMware ESXi host's DiskLib API consolidates disk-flat.vmdk with disk-000001-delta.vmdk. Meanwhile, the virtual machine continues writing to disk-000002-delta.vmdk.

After completing the consolidation of the snapshot, the ESXi host consolidates the Consolidate Helper disk-000002-delta.vmdk with disk-flat.vmdk.

The Virtual Machines are stunned for the duration of the consolidation. In typical circumstances, this process is completed almost immediately. A VM with considerable amounts of delta gathered in the temporary snapshot are stunned for a noticeable or disruptive amount of time. This can have adverse effects on guest applications or services.

When all delta information recorded in disk-000002-delta.vmdk has been committed to disk-flat.vmdk, disk-000002-delta.vmdk and its descriptor file disk-000002.vmdk are removed from the datastore. The virtual machine continues from its base disk or selected point.

For example, in the vmware.log file of the virtual machine, you see entries similar to:

2017-06-10T23:08:57.330Z| vcpu-0| I120: DISKLIB-CHAINESX : ChainESXOpenSubChain: numLinks = 1, numSubChains = 1
2017-06-10T23:08:57.330Z| vcpu-0| I120: DISKLIB-CHAINESX : ChainESXOpenSubChain:(0) fid = 71989930, extentType = 0
2017-06-10T23:08:57.330Z| vcpu-0| I120: DISKLIB-LIB   : Resuming change tracking.
2017-06-10T23:08:57.331Z| vcpu-0| I120: DISKLIB-CBT   : Initializing ESX kernel change tracking for fid 71989930.
2017-06-10T23:08:57.332Z| vcpu-0| I120: DISKLIB-CBT   : Successfully created cbt node 2b9e7eac-cbt.
2017-06-10T23:08:57.332Z| vcpu-0| I120: DISKLIB-CBT   : Opening cbt node /vmfs/devices/cbt/2b9e7eac-cbt
2017-06-10T23:08:57.332Z| vcpu-0| I120: DISKLIB-LIB   : Opened "/vmfs/volumes/5d6553bc-7efb6b6c-19b9-00505601301f/disk/disk-000002.vmdk" (flags 0x18, type vmfsSparse).
2017-06-10T23:08:57.332Z| vcpu-0| I120: SnapshotVMXNeedConsolidateIteration: Size of helper disk '/vmfs/volumes/5d6553bc-7efb6b6c-19b9-00505601301f/disk/disk-000002.vmdk' = 1048576 bytes, approx. time required for consolidating helper disk = 0.263418 sec.

Notes:

Additional RDP session may drop during a long snapshot, this is expected behavior.

The reason the Virtual machine may become unresponsive is because of the stun process integrated with Consolidation process. The stun/freeze happens to accommodate the changes to be written back to the base disk from the Delta disks. At times if the virtual machine is generating a lot of I/O or the underlying storage is experiencing latency, the stun time can increase. In ESXi, it predetermines how long the stun goes, and if it detects it takes more than 15 seconds, it waits for another Iteration, it keeps doing that for 10 iterations. On the 10th iteration, it stuns the virtual machine for the required period of time it needs to. This process has changed and if the process detects that it is over 15 seconds, after 9th iteration it stops trying and cannot delete the snapshot.

Now that being said, simple reasons why the VM would have frozen for long time is either underlying storage latency or simply there were too many I/Os at the time to write back.

Related Information

Understanding virtual machine snapshots in VMware ESXi and ESX (1015180).
Best practices for virtual machine snapshots in the VMware environment (1025279).
Virtual machine becomes unresponsive or inactive when taking memory snapshot (1013163).
Delete all Snapshots and Consolidate Snapshots feature FAQ (1023657).
Estimate the time required to consolidate virtual machine snapshots (2053758).

For translated versions of this article, see:

Español: Por qué la eliminación de una instantánea puede detener una máquina virtual por mucho tiempo (2046709)

Português: Por que a remoção do instantâneo pode parar uma máquina virtual por um tempo prolongado (2045115)

日本語: スナップショットの削除で仮想マシンが長時間停止する可能性 (2079323)

简体中文: 为什么快照移除会使虚拟机长时间处于停止状态 (2075633)

Detectable by VMware SkylineTM

Actions

Copy

link to clipboard
copied!

Print

Language:
Chinese (Simplified)Portuguese (European)JapaneseSpanishEnglish

Attachments

Additional Resources

No results for undefined

Ask The Community

Get answers quickly from VMware experts in the community

Post Subject

CONTINUE IN COMMUNITIES

Related Products:

VMware vSphere ESXi

Related Versions:

VMware vSphere ESXi 7.0.0

VMware vSphere ESXi 6.7

VMware vSphere ESXi 6.5

VMware vSphere ESXi 6.0

Take Our Survey

Was this article helpful?

YES

NO

Copyright © 2005-2024 Broadcom. All Rights Reserved. The term “Broadcom” refers to Broadcom Inc. and/or its subsidiaries.

Terms of Use

Your California Privacy Rights

Privacy

Accessibility

Cookie Settings

Support Assistant