VMware Horizon Community
Ivan_Drago
Contributor
Contributor

Linked Clone limitations?

What are the limitations of linked clones. Can I deploy 100 clones, and have all them being used at the same time with out performace degradation? Does any one know if there any guides (besides the regular documentation) on using linked clones?

Thanks.

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jguzmanr
Enthusiast
Enthusiast

When I was looking into linked clones, I asked vmware the very same question. Their answer was 1000 with no issues. Of course I never tested that number.

chrwood
Contributor
Contributor

I would tend to lean towards the easy out of your mileage may vary depending on HW and cluster size along with the guest o/s and it's specs. If you use vista, 02k7 especially large ost files from exchange this is all I/O related so be sure to beef your SAN and network up. Also take a look at your client machines, if you use TCX for wyse terms this will make the end user experience much better vs RDP.

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Ivan_Drago
Contributor
Contributor

I understand that physical hardware is a limitation. You can't run 1000 clones on 1 ESX box. My question was more of the fact that each clone is using 1 VM/snap shot at the same time. So at one point that has to come into play. I wondering at what point it does. I am doing a windows XP standard clones. and I am keeping it under 100.

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lamw
Community Manager
Community Manager

In terms of limitations, it'll probably be based on the hardware you have and the storage. There are few architectural documents/diagrams regarding deployment of VMware View that may help you in the design.

In general, Linked Clones is based off of the fact that you have a single base image that multiple Linked Clones are pointing to for read access and each LC has a snapshot which then has any new changes directed to their delta file. What you'll notice is now all the writes are going back to each LC which can be distributed across multiple datastores for load-balancing, though all read are still directed back to your main image. This can be an issue if you're creating say 100+ LC off of one image, in VMware View, the base image is actually cloned and renamed as a replica then the LC's will actually be built off of these replica master images. This then allows for distributed read/writes and when you spread the load across multiple datastores. There are some policies that you can setup in View to allow you to revert the LC once a user has logged off which ensures the delta/snapshot will not grow too large but this again depends on what your users are doing and when you refresh/revert the individual image. More details on managing LC's can be found in the documentation along with architectural documents.

If you're interested in playing with Linked Clones technology, we wrote a script last summer that does exactly this and UCSB ResNet is actually using this technology/methodology in production today with about 30+ student computer labs. This will allow you to get a feel for Linked Clones technology and see if it's a viable solution for your end-users, though if you're looking at both provisioning and management, View is a definitely a great product though it does have certain requirements you'll need to fulfill such as running lastest ESX(i) 3.5u3, vCenter, etc whereas our requirements are a little more relaxed but you don't have the advanced management capabilities as View.

Linked Clones for Classic ESX - http://communities.vmware.com/docs/DOC-9020

Linked Clones for ESXi - http://communities.vmware.com/docs/DOC-9202

UCSB ResNet VDI Implementation - http://communities.vmware.com/docs/DOC-9201

=========================================================================

William Lam

VMware vExpert 2009

VMware ESX/ESXi scripts and resources at:

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admin
Immortal
Immortal

Using View Composer there is a limitation of 8 hosts in one cluster.

A best practise is to have 64 LC on one replica! One replica is created per datastore.

Blog: http://communities.vmware.com/blogs/dommermuth

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