ChevUribe
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VSAN with SRM inquiries

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1. SRM can only be installed on a WIndows based vCenter? or it can work between Windows based and Appliance based vCenter?

2. In the event that we will be using VSAN, I can only do vSphere replication to replicate from production to recovery site? Anyone can suggest where can I place my placeholder datastore? Can I have it as a seperate disk on my local server or it must be on a SAN attached storage? If it can be on a local storage, can I use one single placeholder datastore residing on one host for the whole VSAN cluster or I will need to have seperate placeholder datastore per host in the VSAN cluster?

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kermic
Expert
Expert

Yes, you can have vSAN hosting your VMs on protected site and vSAN being used as target datastore for vSphere Replication on DR site. You may also use the vSAN datastore on DR site as placeholder datastore, however in this case, as Mr. Khalsa pointed out "you would want to make sure your replicas are placed in folders and your placeholders in another folder."

Alternatively you could use another shared datastore on DR site for placeholders, assuming you have one. This would make management and configuration easier but might be associated with extra cost.

Putting placeholder VMs on local / non-shared datastore, if my memory serves me correctly, would result in VMs starting up only on host(-s) that can see the placeholders, when you press the red button. Therefore normally it is suggested to put placeholder VMs on shared datastore.

Hope this helps.

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vbrowncoat
VMware Employee
VMware Employee

1. SRM is installed on a 64 bit windows OS. It will work with either a Windows or virtual appliance based vCenter. I would not recommend installing it on the same OS as vCenter.

2. The placeholder datastore can be placed on VSAN along with the replica VMs. To do this you would want to make sure your replicas are placed in folders and your placeholders in another folder.

shivaprasada
VMware Employee
VMware Employee

For placeholder VMs: It is recommended to use a shared datastore. We can still continue to use vSAN datastore as a placeholder datastore.

ChevUribe
Expert
Expert

For placeholder VMs: It is recommended to use a shared datastore. We can still continue to use vSAN datastore as a placeholder datastore.

- so I can have a VSAN cluster in primary location that is replicating on a VSAN cluster in the disaster recovery location via vSphere Replication and the VSAN cluster on the disaster recovery site has a shared storage that is used only as placeholder datastore ?

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kermic
Expert
Expert

Yes, you can have vSAN hosting your VMs on protected site and vSAN being used as target datastore for vSphere Replication on DR site. You may also use the vSAN datastore on DR site as placeholder datastore, however in this case, as Mr. Khalsa pointed out "you would want to make sure your replicas are placed in folders and your placeholders in another folder."

Alternatively you could use another shared datastore on DR site for placeholders, assuming you have one. This would make management and configuration easier but might be associated with extra cost.

Putting placeholder VMs on local / non-shared datastore, if my memory serves me correctly, would result in VMs starting up only on host(-s) that can see the placeholders, when you press the red button. Therefore normally it is suggested to put placeholder VMs on shared datastore.

Hope this helps.

ChevUribe
Expert
Expert

Yes, you can have vSAN hosting your VMs on protected site and vSAN being used as target datastore for vSphere Replication on DR site. You may also use the vSAN datastore on DR site as placeholder datastore, however in this case, as Mr. Khalsa pointed out "you would want to make sure your replicas are placed in folders and your placeholders in another folder."

Alternatively you could use another shared datastore on DR site for placeholders, assuming you have one. This would make management and configuration easier but might be associated with extra cost.

Putting placeholder VMs on local / non-shared datastore, if my memory serves me correctly, would result in VMs starting up only on host(-s) that can see the placeholders, when you press the red button. Therefore normally it is suggested to put placeholder VMs on shared datastore.

Hope this helps.

- By my own point of view, it means that I can have my VSAN datastore in the primary site replicating via vsphere replication to the DR site VSAN datastore which can also SIMULTANEOUSLY working as a placeholder datastore; right? I'll just have to create separate folders for my replicated VMs and for the placeholder VMs? Will there be data corruption or conflict with this? Does it means that SRM can see up to folder level inside the datastore if I have to configure this? because from my understanding, it will just see the datastore.


Thanks!

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kermic
Expert
Expert

Yes, you may use vSAN datastore as replication target for VR and as placeholder datastore for SRM at the same time. Here is some more info on configuring VR to replicate to vSAN: Using vSphere Replication with Virtual SAN Storage

As for the SRM access to the datastore - SRM does not really manipulate datastores directly. It does the thing via vCenter therefore anything that vCenter has access to (more specifically the permissions / roles you give in vCenter inventory) will be accessible to SRM users / processes.

As for the potential data corruption, I think I can see where your thoughts are going. Quote from SRM Admin guide: "Selecting the same datastore for placeholder virtual machines as you use to contain the replica virtual machines that vSphere Replication creates can cause problems when you run reprotect." Not sure at the moment what kind of problems exactly (anyone eslse reading this have tried out this scenario / could share some comments?). And a quick google around did not give me enough info as well. Clearly need to try it out. Hopefully I will have some time and computing power available next week for this. Will definitely post back my results once I have got to some conclusions.

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vbrowncoat
VMware Employee
VMware Employee

The key thing you are trying to avoid by putting the VR target replicas in the same folder as the placeholders is the confusion of having multiple folders with similar names. If they are placed in the same folder SRM has intelligence built in so it will name placeholder VM folders with a "_1" appended to the name so there will not be any overwrite or chance of corruption. The issue is that it will be confusing having multiple folders with similar names hence the recommendation to keep them in separate folders.

It may not be possible to specify a folder for placeholder VMs (I don't currently have access to a VSAN to test), however it is definitely possible to place replicated VMs in a folder.

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kermic
Expert
Expert

Thanks Gs!

I don't think you can specify a folder for placeholders, at least I've never seen that option in SRM GUI (maybe some advanced parameter / cmdline magic...?).

Anyway, developing further the thoughts about "potential issues on reprotect", am I thinking the right direction when assuming that:

1) 2 sites, vSAN is the only datastore on each site so it is used on site A to host VMs and on Site B to hold replicas and placeholders

2) When configuring VR to B we send the replicas to specific manually created folder(s)

3) On B SRM creates placeholders when I'm setting up protection and does it in root of vSAN datastore

4) A loses power and we do a failover

5) A comes back to life and we'd like to reprotect

6) since vSAN is the only datastore on A, I'm gonna need to specify it for placeholders and, if I'm correct, this is where things could get messy as the original VMs on A were in root of vSAN datastore, not in folder as in B. Therefore here the new placeholders created on A during reprotect operation might clash with original VMs (now seeds for reverse replication).

Could this be the reason for that "potential issues on reprotect" statement in documentation?

Anyway, I'd really like to try this out and definitely will do that as soon as I have some time and horsepower.

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vbrowncoat
VMware Employee
VMware Employee

That is correct. Keep in mind that as I stated before the "potential issues on reprotect" are confusion in having multiple folders in the same location with similar names.

To prevent this you would have to look at moving the VMs at your primary site into folders.

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ChevUribe
Expert
Expert

any updates if having VSAN datastore as replicated and placeholder datastore is feasible?

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vbrowncoat
VMware Employee
VMware Employee

I'm not clear what you mean. VSAN works with vSphere Replication and as outlined above the placeholder datastore can be placed on VSAN.

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ChevUribe
Expert
Expert

how can i separate my vsan VMs and my placeholder datastore if I'm using one VSAN disk pool?

From my understanding, VSAN pools all disks into one datastore.

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