operation of snapshot and replica file

[baber]

Dear all

Hi

i have a few questions :

1 - in all of vmware documents said don't keep snapshots more than 3 - 4 days but here in horizon view in link clone mode we have to use snapshots  exactly why we have to use snapshot ? what is that benefit of use snapshot ?

2- what is replica file ? what do it do ?

Best regards

[npadmani]

1 - in all of vmware documents said don't keep snapshots more than 3 - 4 days but here in horizon view in link clone mode we have to use snapshots  exactly why we have to use snapshot ? what is that benefit of use snapshot ?

since you are referring Horizon View, all you are talking about is Linked Clones. The technology is base on Snapshots for sure but here also we have operations like refresh/recompose/rebalance which are going to make sure that linked clone delta which is anchored with particular replica gets renewed time to time. (what I have explained is more associated with Refresh operation of linked clone)

some references to read:

Types of Clone: Full and Linked

VMware Instant Clone Technology for Just-In-Time Desktop Delivery in Horizon 7 Enterprise Edition - ...

Linked-clone lifecycle in VMware View Manager 4.5 and later releases (1021506) | VMware KB

2- what is replica file ? what do it do ?

Replica VM is a full clone copy of Parent VM which is prepared to create linked clones from it. when we initiate first linked clone to be deployed, a full clone copy of Parent VM gets created which is Replica VM, and a linked clone gets anchored with this replica. all the sub-sequent Linked clone gets liked with this same replica. In case of Non-Tiered storage backing your desktop pool, each and every datastore will get a copy of replica VM, while on a tiered datastore backing desktop pool, only one copy of Replica will be residing on flash storage later of tiered storage.

[baber]

i have read all of these but i am still confused about snapshots :

i get snapshot from my virtual machine (parent virtual machine has 100G disk space) and then create 5 link clone desktop now i have 5 desktop that each of them has 100G disk space realy from my datastore space have to decrease 600G but decrease less that this for example 100G now i want to know realy each of my user desktops has 100G disk can transfer 100G data on each desktop ?

what is snapshot roles here? (what is parent vm roles here?)

any data change on my desktop save on parent vm ?

for

  Benefits of Linked Clones

said this :

Another benefit of linked clones is that they are easier to share. If a group of people needs to access the same virtual disks, then the people can easily pass around clones with references to those virtual disks

what is that means exactly ?

i am realy confused

[baber]

can anyone help me ?

[mittim12]

The snapshot is what the replica is based on and then the linked clones are built from the replica.   You could in theory store 100GB of data on each clone but that would end up negating the space saving features of composer and linked clones. 

[baber]

thanks

but can you help me more clearly realy could not find clear document about this architecture

1-in link clone mode we have to use snapshot and it create a replica file still could not understand what will do this replica machine exactly if this machine not create what will be happen ?

2-what will do exactly snapshot file ?

3-my gold machine has 100G thick provision disk but when create for example 10 desktop with link clone each of desktops will be use about 20G from datastore my question is why each dsktop just use 20G space from datastore?

4-if my desktops data increase more than 20G what will be do ?

[mittim12]

1:  The replica is a read only copy of the snapshot that the linked clones will be based on.   If it fails to create then you will not be able to provision any linked clones.

2:  The snapshot is what the replica is based on.

3:   The clones use the replica as their primary source of information and then write the changes back into their disk.    So they may start out as 20 GB but the longer they are around the more changes will be made and the more they will grow.

4:  They will just continue to grow.   It's always best practice to have some kind of refresh schedule.  When you refresh a linked clone it resets it back to the replica.  

[baber]

so thanks

but have a few questions :

1- about replica file understand it will create through snapshot file and base of my linked clone desktops is this machine(replica machine) is this correct?

2- about replica machine you said this is read only what does your means here from readonly machine? is your means that if i power on that can not copy any file on that ?

3 - about disk usage for example when all of my desktops used 20G disk space because my replica machine used 20G disk space from 100G ?

4- this kind of disk space is similar thin provisioning  ?

[baber]

‌can you help me?

[baber]

‌why anyone can not help me?