vSphere5.7.2.管理VM 下

快照功能介绍

snapshots provide administrators with the ability to create point-in-time snapshots of a virtual machine.vmware administrators can then revert to their pre-snapshot state in the event the changes made since the snapshot should be discarded.or,if the changes should be preserved,the administrator can committhe changes and delete the snapshot.(保留机器时间点配置)

创建快照

the option labeled snapshot the virtual machine's memory specifies whether the ram of the virtual machine should also be included in the snapshot.when this option is selected,the current contents of the virtual machine's ram are written to a file ending in a vmsn extension.

the option labeled quiesce guestfile system(needs vmware tools installed)controls whether the guest file system will be quiesced-or quieted-so that the guest file system is considered consistent.this can help ensure ensure that the data within the guest file system is intact in the snapshot.

开机的快照需要做内存快照,恢复时候也是开机状态.比较耗费资源.静默快照关键状态,先停用数据对硬盘读写，恢复时使关机状态.

创建快照"first"

写入大量数据

增量数据会被写入new-2008-000001.vmdk

创建快照"secondary"

复制文件

增量数据会被写入new-2008-000002.vmdk

创建快照"third"

恢复到快照"first"

快照的影响

despite the storage efficiency that snapshots attempt to maintain,over time they can eat up a considerable amount of disk space.therefore,use them as needed,but be sure to remove older snapshots on a regular basis.also be aware there are performance ramifications to using snapshots.because disk space must be allocated to the delta disks on demand,esxi hosts must be allocated to the delta disks on demand,esxi hosts must update the metadata files (sf files) every time the differencing disk grows.to update the metadata files,luns must be locked,and this might adversely affect the performance of other vms and hosts using the same lun.(做内存快照会严重消耗内存空间,建议删除比较老的快照,每次快照都会更新原文件，会对lun盘符锁定,在这一瞬间所有的vm都不能读取这个lun)

模板技术的局限

templates are a great way to help standardize the configuration of your vms while also speeding up the deployment of new vms.unfortunately,vcenter server doesn't make it possible for you to transport a template between vcenter server instances or between different installations of vmware vsphere.to help address that limitation,vmware helped develop a new industry standard:the open virtualization format(ovf)standard.(不能够传递一个模板在两个vcenter之间,那个vcenter下的模板只能在这个下面使用不能到给别的vcenter）

ovf技术介绍

open virtualization format (formerly called open virtual machine format)is astandard format for describing the configuration of a vm.while originally pioneered by vmware,other virtualization vendors now support ovf as well.vmware vsphere 5 provides ovf support in two different ways:(开放式虚拟化格式,用来描述一个vm配置）

1.deploying new vms from an ovf template(essentially,importing a vm in ovf format)（导出ovf)

2.exporting a vm as an ovf template

ova与ovf

ovf templates can also be distributed as a single file.this single file ends in .ova and is in tar format, and the ovf specification has strict requirements about the placement and order of components within the ova archive. all the components that i've already described are still present,but because everything is stored in a single file,it's more difficult to view them independently of each other.however,using the ova(single file) format does make it easier to move the ovf template between locations because there is only a single file with which to work.(对原始ovf做压缩成ova,ova是一个文件拷贝比较方便)