With the widespread application of virtualization, the maintenance and troubleshooting of virtual machines have become part of the daily work of operations personnel, such as VMware network optimization, PowerVM backup, centralized management of PowerVM, and handling failures like Citrix application not responding.The following are some operational experiences shared by community members for your reference.
1. What is the most critical aspect of operating a virtualization platform?
The key points in operation are:
1. Efficiency
This mainly depends on the scale of your virtualization platform. If the scale is relatively large, using scripting methods like Python and PowerCLI (for VMware only) will be very convenient, allowing you to perform operations such as creating, modifying, and deleting related resources like virtualization control centers, hosts, virtual machines, virtual networks, and storage, especially for batch operations, such as batch creation of virtual machines.
For those with capability, automation configuration tools like Puppet and Ansible can be used for daily operational tasks on virtual machines;
2. Global Control Anytime, Anywhere
This mainly relies on monitoring and logs, such as Zabbix, ELK, or commercial versions, to understand the health status of the virtualization platform and respond accordingly;
3. Security
This mainly pertains to virtual machine and data backups; even if the virtual machine or data is damaged, backups are available for recovery.
2. Virtual Machine Backup Capacity and Snapshot Principles
When you create a snapshot of a virtual machine, it is a specific file. It is also a redo-log log. The delta file is a change bitmap on the base VMDK (virtual machine disk), so it cannot grow larger than the VMDK. Each time you create a snapshot for a virtual machine, a delta file is created. When the snapshot is deleted or restored in the snapshot manager, these files will be automatically deleted.
These files are used to store metadata and information about the snapshot. This file is in text format and includes information such as the snapshot display name, UID (number), and disk file name. Before you create a snapshot of the virtual machine, the initial size of this file is 0 bytes. Thus, once a snapshot is taken, this file will grow and be continuously updated.
After the snapshot is removed, this file cannot be completely cleared. Once you delete a snapshot, it will still leave a position in the file for each snapshot, but only increase the number and place the name in the “Consolidate Helper,” which may be used to consolidate the backup *.vmsn file.
This is the snapshot state file, which stores the precise running state of a virtual machine when using a snapshot. The size of this file depends on whether you choose to retain the storage of this virtual machine as part of the snapshot. If you choose to retain the virtual machine’s storage, then this file will be larger, maximizing the RAM allocated to the virtual machine.
This file is similar to the VMware suspended state file .vmss. Each snapshot of a virtual machine will create a .vmss file; these files are automatically deleted when the snapshot is moved.
In most cases, you should avoid creating multiple snapshots for the same virtual machine; each time a new snapshot is created, the system’s speed will slow down. Each snapshot will create a corresponding delta disk file, and if the virtual machine needs to read multiple delta files, it will inevitably increase the system’s I/O load. This process will undoubtedly extend the response time of the virtual machine and generate additional disk operations.
If you only want to save the latest version among a series of snapshots, you can consolidate them into a single snapshot. This method can help improve system speed and management efficiency. Select the target virtual machine, right-click, and then choose to consolidate. You can check whether the virtual machine needs consolidation in the virtual machine and template view, and all virtual machines that need to be consolidated will be displayed in the list.
3. How to Optimize VMware Network Design for High Availability?
For high availability of compute nodes, it is important not only to ensure redundancy in resource quantity but also to set policies properly. Here are a few points to consider:
1. Admission Control Policy: For production environments, it is generally considered appropriate to choose (Host Failure the cluster tolerates =1), but if your resources are very idle, you can appropriately increase this.
2. Set the boot priority (high, medium, low) for virtual machines on each physical machine according to their importance.
3. When the number of virtual machines on a physical machine far exceeds the number of physical machines in the cluster, consider setting virtual machine HA mutual exclusion rules.
4. In production environments, try not to set the DRS policy too aggressively. Especially when there are load balancing devices in front, it is recommended to set DRS to advisory mode.
For storage, it is essential to ensure that all nodes in the cluster see the same view of external storage, which must be fully shared to ensure HA and DRS functionality. Additionally, regarding storage, consider the following points:
1. In the volume properties, set the Storage IO Control option to Disable. It is not recommended for VMware to interfere with the underlying IO, as this may introduce performance risks.
2. Set the multipath policy for the volume to Round Robin.
VMware offers both VMware HA and FT for high availability, but they can only achieve fault monitoring and recovery at the ESXi host level. Generally, high availability is implemented at the application level, using appropriate clusters or load balancing according to different business roles. For backend database roles, it is generally deployed on physical machines; if it must be on virtual machines, consider using Veritas’s InfoScale series of clustering software (formerly VCS), which can interact with VMware’s vMotion and other management methods without requiring bare devices to avoid split-brain scenarios, and supports applications with different priorities to start and stop in a specified order. Similar clusters can only achieve basic functionality.
4. VMware Escape Issues
Virtual machine escape refers to exploiting vulnerabilities in virtual machine software or software running within the virtual machine to attack or control the host operating system of the virtual machine.
“There is a boundary memory access vulnerability in the drag-and-drop (DnD) feature of VMware Workstation and Fusion. On the operating system running Workstation or Fusion, an attacker can exploit this vulnerability to achieve guest escape and execute code on the host machine. In Workstation Pro and Fusion, if the drag-and-drop and copy-and-paste (C&P) features are disabled, this vulnerability cannot be exploited.”
5. Snapshot Deletion Merging Policy in VMware
[Problem Description]
For example, there is a snapshot A->B->C->current position
When the virtual machine is powered off
Question 1. If snapshot B is deleted, is the content of snapshot B merged into A or C?
Question 2. If snapshot C is deleted, is the content of snapshot C merged into B or the current position?
When the virtual machine is powered on
Question 3. If snapshot B is deleted, is the content of snapshot B merged into A or C?
Question 4. If snapshot C is deleted, is the content of snapshot C merged into B or the current position?
If the rolled-back snapshot does not contain memory state, the server will shut down and use the previous snapshot state upon reboot. If the snapshot includes memory state, the virtual machine will simply pause and then recover to the disk and memory state of the previous snapshot.
When users operate on VMware virtual machine snapshots, they should be aware that when deleting all snapshots of a virtual machine, all created delta files are first merged into the original VMDK file and then deleted. If you choose to delete only a specific snapshot, then only that snapshot is merged into the upper-level snapshot. If you choose to roll back to a snapshot, then the existing disk and memory state will be discarded, and the system will revert to the state at the chosen rollback time point. Regardless of which level of snapshot you choose to roll back to, it becomes the new parent snapshot. The parent snapshot does not represent the latest snapshot; if you roll back to a previous time point, the virtual machine will revert to the state of that earlier time point. In the Snapshot Manager, the parent snapshot is always labeled “You are here,” indicating the current state of the virtual machine.
6. Differences Between PowerVM Backup Methods and Traditional Backups
The VIO Server is essentially a packaged AIX, and it has two backup and recovery methods: one is NIM backup and recovery, but be sure to mark “not as a NIM server client” during recovery; the other is the viosbr command for backup and recovery.
The backup of VIO Clients is the same as traditional backups; the operating system can be backed up and restored via NIM, and others can also use backup software for LAN-free backup and recovery.
In the case of PowerVM not being too much, I think using a tape drive for operating system backup is sufficient. After all, operating system-level backups do not need to be done too frequently. Client partitions can use tape drives, although this will involve many device mapping operations, which can be cumbersome. A virtual image library can be created on VIOS.
7. How to Achieve Centralized Management with PowerVM?
PowerVC is developed based on the OpenStack architecture, which can manage PowerVM, achieving graphical quick deployment and maintenance.
8. How to Dynamically Add a Hard Disk for Mirroring in PowerVM Without Downtime in Production Environments?
In fact, doing mirroring in PV is essentially mirroring at the LV level in PV, which can be queried using lspv -l hdisk0,hdisk1. For example, when mirroring the rootvg, there is a dumplv mirror. In an already created mirror of rootvg, a new LV can be created, which by default does not select synchronization, meaning that this newly created LV will only be established in one PV, while the other PV does not have this LV.
9. How to Resolve Issues with Applications Published on Citrix Platform Not Being Usable?
When finding that applications published on Citrix cannot be used, logging into the Citrix client shows a CGP error. Logging into the Xenapp server checks the log error source from the Reliability Server, described as Unable to connect to the CGP tunnel destination (127.0.0.1:1494). The server had a record of automatic reboot the previous night. Everything was normal the day before, and it was suspected to be related to system upgrade patches. I chose to uninstall all the patches updated the day before, reboot the server, and then tested Citrix, and everything worked normally. Since I was in a hurry, I did not uninstall each patch one by one for testing, and I initially judged that it was most related to the .NET patch. Subsequently, I disabled the automatic updates of that server.
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