Best practices - Celerra configuration for VM datastores

Question

I have read all the best practices documents I can find and haven't seen a clear answer to how to best configure file systems and iSCSI targets for a VM Infrastructure. I realize that there is no one clear answer, I am just looking for advice based on other user experiences.

For example, lets say I have 3 ESXi servers and 10 VM hosts. I will be using iSCSI to connect to the Celerra for storing the VM datastores/VMFS. One of the hosts is an email server, one is a SQL server and the rest are mostly file/application servers.

How best to set up file systems on the Celerra? I could create one file system with 1 iSCSI LUN/Target located on that file system. Then I could create 1 datastore on that LUN to hold all the VM's. I have read a number of reasons why this in not the best idea due to number of TCP connections, IOps needs of the datastores and queue depths.

I could create 1 file system with multiple iSCSI LUNs on it, each with a datastore, or multiple file systems with an iSCSI LUN each (each with own datastore).

It seems to me the best solution would be to have multiple file systems, preferably in different storage pools, each hosting a datastore. In the example above, I would probably create two or three file systems, each with it's own datastore, each hosting multiple VMs.

Long winded...just thinking out loud I guess. But any input based on experience would be appreciated.

SAMEERK1 · Answer

Hi,

This document will be helpfull for you.

You can find White Papers at this location on Powerlink:

Home > Support > Technical Documentation and Advisories > White Papers > All White Papers

Cheers,

Sameer Kulkarni

http://powerlink.emc.com/km/live1//en_US/Offering_Technical/White_Paper/h6370-vmware-infrastructure-deployment-celerra-wp.p

GlennAnders · Answer

I have read this doducment but it really does not address my question.

Rainer_EMC · Answer

It really depends on your size and I/O requirements

best-practices are fine and best followed if you have enough disk

there is also always the tradeoff between I/O seperation and flexibility

sure there are performance reasons for multiple LUNS/targets/data stores - but IMHO for smaller setups its not worth the hassle in terms of administration.

Also the more you "fragement" you storage space the more likely you end up with running out of space in one area while others still have plenty

personally I would:

- if you have a small Exchange Server (less than 500 users) dont worry much about the backend layout

- larger than that go with the building blocks in the solution

- put multiple ISCSI LUNs in one file system to get the benefits of sharing free space

- use virtually provisioned ISCSI LUNs if you plan to do snapshots or replication

I would also take a good look at using NFS instead of ISCSI for the VMWare data stores - much easier to setup and more flexible

Rainer

BillStein-Dell · Answer

I would also take a good look at using NFS instead of ISCSI for the VMWare data stores - much easier to setup and more flexible

Rainer's advice, as usual, is excellent, but I'm not 100% sure about NFS over iSCSI. This, too, depends on the environment. There are some issues with using NFS for VMs when it comes to performance, so I would suggest that for your highest I/O-intensive VMs, go with iSCSI. Less packet overhead, but not as easy to set up and not very flexible. Use NFS for all of your other VMs, as it is much easier to maintain.

Rainer_EMC · Answer

dynamox wrote:such a corporate response, where is my 'Helpful' button.sorry - I thought you knew that there are strict rules about mentioning roadmap and futures in the public.(not at least due to the US SEC)If you need larger than 2TB ISCSI LUNs than I suggest to use Clariion native ISCSI.Rainer

Rainer_EMC · Answer

For futures please talk to your local EMC technical contact Rainer

dynamox · Answer

Celerra's iSCSI limit of 2TB is a deal breaker for us. Any idea when it will be increased ?

Rainer_EMC · Answer

I would like to understand why its important to have LUNs larger than 2TB

I thought unless you use RDM you would would put a data store on multiple LUNS and it wont matter much

Rainer

P.S.: You can also use Clariion native ISCSI for LUNs larger than 2TB

dynamox · Answer

RDMs , I don’t like VMFS datastore span multiple storage objects.

dynamox · Answer

If you need larger than 2TB ISCSI LUNs than I suggest to use Clariion native ISCSI. not on my integrated NS80

dynamox · Answer

such a corporate response, where is my 'Helpful' button.

Celerra

Best practices - Celerra configuration for VM datastores

Was this post helpful?