Best Senario for Virtual machine distribution among SAN LUNs and Replication fail over Senario

[osamai9]

What the best Best Senario for installing VMs on Big LUNs or each VM on dedicated LUN:

we planninig to implement 70 VMS on 7 Esx 3.5 Servers with Replication LUNs usisng HP CA .

using 4 Big LUNs 800GB datastore on SAN RAID 5 ( each LUN will contains 16 VMS ) ? or each VMS will deployed in seperate small LUN 50GB datastore on SAN RAID 5 and what this effect on the fail over procedure to the DR Site if we choose BIG LUNs, also if this VM include 3 disks (store them on the same datastore or each disk on different datastore)

Thanks

[Lightbulb]

A certain number of large LUNs is usually how provisioning is addressed. I would go with 6 x 550GB which would allow you to have fewer VMs per LUN

You should save some space on SAN for future growth. Also if you have VMs that will have high I/O file systems you may wish to create one RAID 10 LUN for high I/O. It all depends on what you have to work with budget wise.

[kjb007]

The difference between the two options, as far as replication is concerned, is very little. Whether you choose small LUNs for each vm, or larger LUNs for a handful of vm's, you still have to get the data replicated to the secondary site in its entirety. Small LUNs would obviously be faster in the beginning. Once the datastores have been copied over, you will have to add the replicated LUNs to the ESX hosts at that site, and register each vm. SRM would do this for you, provided you have SRM license. It is generally a good practice to have a LUN large enough to hold 10-15 vm's.

-KjB

VMware vExpert

[osamai9]

thanks KJB for your post yes it is replication concern .but what hapend if the connection between two site is not fiber connection it is FCIP connection so we will use async mode not sync .also when we use one LUN with 15 VMs whats happend if we want only one VM to be replacted fast or to force copy to distenation site, then to fail over this VM to the secondary site (not all VMS).

also can we register the VMs on secondary site one time after first replication manually, we are not plan to use SRM in this stage.

[kjb007 · Accepted solution]

Remember that the vm's are a set of files, and those files live in your datastore. If you have a large datastore with many vm's, then you will have to replicate the entire datastore to the alternate site in order to get at that data. You can't really use SAN-based replication for just the single vm in a larger datastore. SAN-based replication isn't really aware of what is stored on it, it just replicates the blocks that it knows about. You can copy the vm files individually as well, but that's more of a copy and not replication. Otherwise, if you're concerned about some vm's vs others, then using smaller LUNs would work better for you, or use tiered datastores to replicate the vm's that are important for you, and put the rest in a larger datastore.

FC/FCIP/IP does not really matter. As long as the one array can talk to the other, you're fine. Our secondary site is hundreds of miles away, and we replicate just fine over IP, from one array to another.

Yes, without SRM, you will have to register the vm's manually one at a time, or write a script to work through all of them.

-KjB

VMware vExpert

[osamai9]

so SAN based replication is it ok to replicate the VMs,without SRM if we right scripts fro VMS registrtion

whats type of replication in your senario is it SAN_based or just through VMware SRM.

[kjb007]

SRM does not do the actual replication. It facilitates the replication. It is still array-based replication underneath. I don't currently use SRM in my prod/dr environment, and do my replication as I described above.

-KjB

VMware vExpert