In my new place, VM admin is running few VMs with more than a month old snapshots. Everything are running ok as far as they concern. These are small appliances. I read VMware article and it says that not to keep more than 72 hours, but, it did not to mention the serious issue by keeping the snapshot other than the data store space.
Can we keep the VM with snapshot for long time? if not, what will happen other than snapshot size?
The best practice to keep it consolidated within 72 hours once the job is completed for which the snapshot is taken. Please read the below URL which helps a lot for more info
Multiple snapshots are not simply a way of saving your virtual machines. With multiple snapshots, you can save many positions to accommodate many kinds of work processes.
When taking a snapshot, the state of the virtual disk at the time the snapshot is taken will be preserved. When this occurs, the guest cannot write to the vmdk file. The delta disk is an additional vmdk file to which the guest is allowed to write. The delta disk represents the difference between the current state of the virtual disk and the state that existed at the time the previous snapshot was taken. If more than one snapshot exists, delta disks can represent the difference (or delta) between each snapshot. For example, a snapshot can be taken, and then the guest could write to every single block of the virtual disk, causing the delta disk to grow as large as the entire virtual disk.
When a snapshot is deleted, the changes between snapshots and previous disk states are merged, and all the data from the delta disk that contains the information about the deleted snapshot is written to the parent disk and merges with the base disk only when you choose to do so. This can involve a large amount of disk input and output. This may reduce the virtual machine performance until consolidation is complete.
The amount of time it takes to commit or delete snapshots depends on how much data the guest operating system has written to the virtual disks since the last snapshot was taken. The required time is directly proportional to the amount of data (committed or deleted) and the amount of RAM allocated to the virtual machine.