How to span multiple LUN's onto One (or less) Datastore(s) in Vmware vSphere ESXi 4.1 environment?

[universalknr]

Hey guys-

I currently have 2 ESXi Hosts (version 4.1u3), 1 vCenter Server, and 1 EMC VNXe3300 SAN (20TB via iSCSI) that make up my virtual environment.

On the EMC VNXe, you create VMware Datastores (which have a limit of 2TB) and then connect these Datastores to the VMware ESXi Hosts.  Once connected, you would continue the process by going through the Add Storage Wizard via VMware to connect the Storage Type of Disk/LUN via iSCSI.  In the end, the LUN(s) would then be accessible by the Virtual Environment (found in Configuration>Storage>Datastores) as typically expected.

Due to the 2TB limit (both on the EMC, VMware Version, & VMFS3) on the Datastores, I am left with having multiple Datastores being created on both the EMC side and the VMware side of things (see attached photo).  I know that this cannot be rectified via the EMC level, but I was wondering if there was anyway for me to join all of these Datastores together on the VMware side of things.  This way instead of navigating to Configuration>Storage>Datastores and seeing 6 separate iSCSI Datastores, there would just be one (or multiple, but less than the existing) Datastore; this would then span across all of the actual Datastores that I would specify.

I do not know what the appropriate terminology is used to describe this, but I would hope that someone would be able to assist me with what I am looking to achieve.  Or at the least, can you please steer me in the right direction.  If this is not something that can be achieved or if it is recommended against, what would be other option(s) that would be recommend?

Thanks for the help.

[rcporto]

You can create a Datastore with multiple extents... the configuration maximum is 32 extents of 2TB minus 512B that will gives you a datastore with maximum sze of 64TB.

I will recommend you take a look at the following links:

VMware KB: Creating and managing extents on ESX/ESXi

Increase VMFS Datastores

[universalknr]

Thanks Richardson.

I took the time to read over both of the provided links, which were very helpful.  This is exactly what I was looking to accomplish.

This leads to a couple questions before I can determine if I should actually do this.  If anyone could chime in, it would be appreciated!

The VMware KB doc states:

Therefore, the best practice is to have one LUN per VMFS only (exception being local storage). When using extents, gather multiple LUNs under one logical VMFS and not multiple partitions per LUN.

1.  I don't understand what they mean by "not multiple partitions per LUN", can you clarify?  The way that I would imagine doing this, is that I would be creating multiple LUN's on the EMC.  Then I would create the Datastore on the VMware Host (example - VMFS01) and then I would add the remaining LUN's as extents (LUN02 & LUN03) to the VMFS01 Datastore.

For adding extents, use one of two methods - Adding a new Extent or Growing an Extent in an existing datastore.

2.  I read the differences here, but is when better than the other?  I am not sure of which to choose or why would I choose one vs the other.  At this point, I would probably choose the Adding a new Extent method.

All VMFS metadata is located on the master extent, which is typically the first LUN on which you created the datastore.  If one of the extents goes offline, its data becomes inaccessible.

3.  As all of my LUNs would be coming from one SAN, spanned across the same RAID Array - it seems obvious that I should create one Datastore and then grow it by adding multiple extents (via LUN's).  So my question, what would be the reason NOT to do this?

[showard1]

Hi

I would avoid messing with extents its probably going to bite you later.

Couple of questions for you:

1.     Can I ask why you're trying to do this?  For instance, is it to simplify placement of new VMs, make backups easier, etc.  Depending on the objective there may be alternate ways to address the need.

2.     What licensing do you have for vSphere?  (standard, enterprise, enterprise plus).

3.     Is there any reason you couldn't upgrade to 5.5?

Thanks

Sean

[universalknr]

Hey Sean-

Thanks for the response, looking forward to your responses.

I am interested in hearing why you suggested to avoid messing with extents and can you clarify on what you meant by going to bite you later?

1.  To be honest, one of the reasons that I am trying to do this is because of the visual aesthetic, there are just numerous Datastores in the Datastores section.  The other reason is because the Datastores are organized by department.  So for example:  All Voice VMs get placed on the Voice Datastore, but because of the 2TB limit, there are multiple Voice Datastores, such as Voice_DS01, 02, 03, etc.  Just doesn't make sense as to why I shouldn't just centralize all of the LUNs into one Datastore.

2.  I am currently running VMware vSphere & vCenter Enterprise Plus, v4.1u3.

3.  Yes, upgrading is not an option at the moment or for the remaining of the year at that.

[universalknr]

Does anyone have any input as to why I should steer clear of Extents or why they are a negative feature to utilize?

[rcporto · Accepted solution]

Take a look here: VMFS Extents - Are they bad, or simply misunderstood? | VMware vSphere Blog - VMware Blogs

[universalknr]

@Richardson Porto

Thanks, this is exactly what I needed to read!

Thanks for all the help here guys, very much appreciated.