In the era of VMware ESX 3, many IT staff have reservations about the use of thin virtual disks, which can grow automatically as write data increases. Everyone thinks that the performance of a thin disk cannot be compared with a "fat virtual disk" with a fixed capacity.
Despite the large number of studies on thin virtual disks show virtually no performance loss. Now VMware is also beginning to support the creation of thin disks in the user interface of vSphere. The use of thin provisioning features needs to be re-planned and has become a popular point of view.
misunderstanding
user thinly provisioned virtual disk thin does not accept the view of the virtual machine will bring a lot of extra pressure IOPS - even though studies have shown that fat The performance improvements that disk can bring are minimal. However, users are still accustomed to using thin disks on virtual machines with little or no IOPS pressure (such as domain name servers and DHCP servers).
I do not agree with this approach. Thin provisioning saves a lot of disk space and saves administrators from worrying about issues such as how much disk space to allocate for virtual machines.
in thin virtual disk not very popular, traditional disk if set too large to bring wasted storage space; will overflow when the space is too small, then virtual machine needed to be increased. This is often encountered in a lab environment where storage is very limited.
thin provisioning to overcome issues related to
This does not mean there is no thin provisioning any potential problems. Thin disks can have disastrous consequences if you don't know enough about traps. For example, it is often the case that a virtual disk is created that fills up the allocated LUN/volume size. Suppose you have created 10 virtual machines, each with a 40GB compact disk. Initially, thin disks consumed only a few megabytes of space, but when these disks were all full, they required 400 GB of physical space. Thus, if the LUN/volume space size is only 350GB, things get very bad.
This is not impossible. There are a lot of seemingly inconspicuous virtual machine tasks that can cause the space on the thin disk to expand rapidly. First of all, please pay attention to how you format the disk inside the Windows system. In Windows, we were told not to use the quick format feature because it would reduce disk read and write performance in many environments.
But if you use full formatting for a thin disk, the process writes to each sector of the virtual disk -- so the space for the thin disk grows quickly to the maximum capacity. This conveys a message: For a thin disk, use the quick format method on Windows systems.
My streamline the disk can not be compressed
streamline some operations may lead to rapid expansion of the disk, including the compression of VMware Tool - for Delete files to free up disk space. Before the virtual machine is created and used as a template, I usually recommend that the user defragment the disk and run the compression function to achieve disk optimization. When
delete file operations in Windows, the data is not actually deleted from the disk. It's just a markup in the file system. In this case, even deleted files will still take up disk space.
Compression is not available for all virtual disk types or operating systems. Depending on the version of VMware Tools you use, it may be disabled in some cases.
consideration of such a process, defragmentation and compression not have any effect on thin plate. Both operations move files around and perform writes, which increases the size of the thin disk. You will also find that compression is not available within the affected virtual machine.
If you have a task progress frequently performed regularly create and delete large files operations, streamline disk so soon grow up, and this part of the remaining space can not be restored to the storage array. So how can we recycle this part of the disk space? The deleted file in the virtual machine can be safely cleared by adding the -c parameter to the SDelete command.
This operation will cause the virtual disk to temporarily increase. But if you use VMware's Storage vMotion and thin disk capabilities, you can compress the virtual disk to the actual size. The process is cumbersome but very effective.
I hope that VMware can add compression to the data storage browsing terminal, including expansion options (this expansion option is used to convert thin disks into fat disks).
With the deepening of VMware and storage partners, the problem can be solved eventually, and add more new features through the vStorage API. In this way, the storage array can know which files in the virtual machine are deleted, and then release the corresponding space to display the actual space size of the disk.
Even so, if the virtual machine creation and deletion of regular, large file operation, still have to adhere to consider the virtual machine virtual disks using fat way.