• Status: Solved
  • Priority: Medium
  • Security: Public
  • Views: 2148
  • Last Modified:

Vmware Snapshots and Thin provisioning

I will appreciate someone's explanation regarding Vmware Snapshots.
1- If I understand , we can take several snapshots of a VM and can revert back to any point in time.
Now regarding the backup of VMs, when VMs are backed up , are the snapshots backed up as well along with VMs? are the snapshots purged from the VMs after back up

2- if I create a VM with a disk of 40GB, and set up the Thin provisioning.  Does this mean  the disk can be filled up to the maximum of 40GB or it can go over 40GB ?

I know it is 2 in 1 question, but it saves time..

I will appreciate your help in advance.
0
jskfan
Asked:
jskfan
8 Solutions
 
Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
Checkout my EE Article

HOW TO: VMware Snapshots :- Be Patient

1. Snapshots are merged into the parent disk after the backup. (snapshot is deleted). The snapshot is the delta in write mode, so only the parent is copied at backup.

2. The snapshot maximum is the maximum size of the parent disk. If you provision a 40GB disk, the max is 40GB.
0
 
SebastianAbbinantiCommented:
Thin provisioning: The VM will only occpy the space it actually needs on the datastore, regardless of the size you give it. There is one issue, once the space is used on the VM, it does not give it back, regardless of whether or not you delete files and free up space.

If you create a VMDK with 40GB, it will only occupy what it uses, up to 40GB. You can increase this after the fact if you OS support extending the partition.
0
 
Paul SolovyovskyCommented:
Keep in mind snapshots are not backups as they rely on the parent disk. Snapshots will also cause a degradation in performance as there are additional read and writes performed due to parent disk being read only.  

Snapshots should only be used for short periods of time, otherwise they cause issues with performance and if one of the delta vmdk's goes bad your entire VM chain may be bad.  When deleting snapshots your performance is decreased even more due to consolidation and make make the VM unusable depending on applications running.
0
Industry Leaders: We Want Your Opinion!

We value your feedback.

Take our survey and automatically be enter to win anyone of the following:
Yeti Cooler, Amazon eGift Card, and Movie eGift Card!

 
jskfanAuthor Commented:
Well, let me see if I understood the Snaps:

1- when you create a VM machine and assign it 80GB disk size ...is this disk called parent Disk?
2- after you create a snapshot, it will create an empty file (vmdk) linked to parent disk, then changes will write to the this empty file, and the parent disk is read only. does the new file(delta) count on the 80GB size or it is not ? I mean it is included in the 80GB?

3- Is there any tool that can report the VMs that have snapshots and preferrably in chronological order ?
- Which VMs (Block level back up) that can delete and commit the snapshots to parent disk ?

4- Regarding Thin provisioning, if I have a VM created and assigned 80 GB and set up as Thin Provisionning, when the data starts filling up the disk,... would 80GB be the maximum that the data can get to or it can use space from the storage
0
 
Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
1. Correct, original VMDK is the parent disk.

2. A snapshot is a delta child disk, linked to the parent disk, it is dynamic in that it can grow, based in the changes being written by the VM OS, but cannot grow larger than the parent disk. Snapshot is additional, so it's not included in the original 80GB.

3. Snapshot Manager. (Right Click the VM, Snapshot Manager). Otherwise you have to use scripts.

See scripts included in the VMware Community Pack
http://www.virtu-al.net/featured-scripts/vmware-powerpack/

4. 80GB is the max.
0
 
jskfanAuthor Commented:
Thanks..

4- Why thin provisioning is most of the time not recommended. It sounds to me just like thick provisioning. You assign disk size for the VM, example :80GB , then the when you add data it fills up the disk up to 80 GB, I don't see how THIN is difference from THICK provisioning..
Any clearance on this ?
thanks
0
 
Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
performance and not supported by vendor OS and Applications.
0
 
jskfanAuthor Commented:
<<performance and not supported by vendor OS and Applications. >>

Other than that, I don't see the difference other than the name Thin /Thick.

Thin= You reserve the Disk size (80GB) when you create a VM
Thick=You reserve the Disk size (80GB) when you create a VM
0
 
Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
But Thin at the start is small and dynamically grows to reach the limit of 80GB.

Thin - At first, a thin provisioned disk uses only as much datastore space as the disk initially needs. If the thin disk needs more space later, it can grow to the maximum capacity allocated to it.

Thick - ALL Space required for the virtual disk is allocated during creation.
0
 
jskfanAuthor Commented:
I am not familiar with THIN provisionning.

When you create a VM and you assign it 80 GB and select thin provisionning.
Now if the disk uses 10GB for OS , then the 70GB will still be reserved to the same VM ?
and as more data is dumped to the disk, the free space will shrink up until all 80GB is used up.

With THICK.. it is the same I guess,,,where is the difference , I still don't see it...unless if my statment is wrong...which means I still don't understand the THIN provisioning yet....
please , provide clear example for THIN and THICK..

I will appreciate it.
0
 
Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
Thin - think of the disk as self expanding up to 80GB. When the virtual disk is created it takes up 0 (zero) datastore space!

 Initially you install an OS, the OS takes up 20GB, so the virtual disk on the datastore takes up 20GB. (but can grow to a max of 80GB).

Thick - When you create the virtual disk, 80GB is taken up and used on the datastore immediately, before you've even installed on OS!
0
 
xcomiiiCommented:
hanccocka is correct. The process of creating a thin disk is also instant, creating a thick disk usually takes a little extra time, due to writing of 0's in the data area.

So advantage of thin disk: Less disk space used upon creating the virtual disk, saving disk space.

The advantage of thick disk: a little bit more faster when you start to write/read to the virtual disk (eg installing an OS, moving files etc), and also some special applications like backup software requires the us of thick provisioned disks.

However, the future tends to be using thin disk all over and I cannot say that the extra increase of speed (very small increase btw)  in thick vs thin justifies the extra disk space used, so I recommend thin disk unless you have some special applications that require thick provisioned disks.
0
 
jskfanAuthor Commented:
Excellent explanation
0

Featured Post

Independent Software Vendors: We Want Your Opinion

We value your feedback.

Take our survey and automatically be enter to win anyone of the following:
Yeti Cooler, Amazon eGift Card, and Movie eGift Card!

Tackle projects and never again get stuck behind a technical roadblock.
Join Now