Understanding storage and VMware vCenter Server components

In this expert podcast, with VMware expert Mike Laverick, we discuss the storage aspects of VMware vCenter Server components.

From the management hub of VMware’s vSphere -- vCenter Server -- an IT administrator can monitor and control many aspects of the virtualization platform running in his data center. Storage is crucial to that environment. But how, exactly, does storage interact with vCenter Server components?

In this podcast, VMware expert Mike Laverick sits down in the studio with us to explain the basics of VMware vCenter Server, formerly called VirtualCenter. He drills down into some of the storage components of vCenter Server, including the vStorage APIs for Storage Awareness, or VASA. He outlines the benefits of Profile-Driven Storage and describes how it interacts with VASA. And finally, he explains the rumors he's heard swirling about vVolumes – a possible feature in the next version of vCenter Server.

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Understanding storage and vCenter Server components

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SearchVirtualStorage.com: Let's start at the very basics. Can you explain to our listeners what, exactly, VMware vCenter Server is?

Laverick: Sure. VMware vCenter Server is the centralized management system that sits at the heart of VMware's … vSphere. It’s a Windows-based system currently, although they now have a Linux-based appliance. It's backed by a Microsoft SQL, Oracle or IBM DB2 database, which is where it stores most of its configuration [information].

For most VMware administrators, I imagine the first thing they do in the morning is crank up their vCenter Server components and have a look at what their environment is doing, to see if they have any alerts, alarms or red exclamation marks on their environment. In short, vCenter Server is the central management point for most VMware admins.

SearchVirtualStorage.com: So which of the vCenter Server components are the ones that impact storage?

Laverick: It won't come as a surprise to your listeners that storage is absolutely critical to any VirtualCenter or VMware environment. At the end of the day, the VirtualCenters you create have to be stored somewhere. From VirtualCenter, a VMware administrator can create new data stores and mount NFS volumes if they've been made available. They’ve also got some controls over the new enlightenments that are being added to the product to make VMware and the core platform storage-aware -- things like vStorage APIs for Array Integration (VAAI) and VASA. In the vSphere 5 release, which shipped just last year, [VMware has] added new features such as storage profiles and data store clusters to the suite of tools available. Looking out to the future, VMware has already started to talk about new storage objects, VVols, as a replacement for the LUNs and volumes we've been working with for the last decade or maybe even more.

SearchVirtualStorage.com: You briefly mentioned VASA; can you explain to readers what that means?

Laverick: It's software that's provided by the storage vendor -- be that EMC, NetApp, HP or Dell – [that plugs] into the VirtualCenter environment and populates VirtualCenter with a whole series of data about what the storage is capable of -- what its RAID levels might be, what its replication status might be, whether it has snapshot space reserve left. It's trying to feed back from the storage layer, up into the hypervisor, greater awareness of what the storage is actually capable of.

The main reason for VASA is to make sure that when a VMware admin creates a new set of virtual machines, or group of virtual machines, called vApps, that admininstrator has real awareness of what the storage is capable of. Rather than just having a label, that VMware administrator can know whether that’s SSD storage, whether it's replicated or not, whether it supports the snapshot mechanisms. All that useful information is critical in making sure that the right VMs go in the right type of storage.

SearchVirtualStorage.com: You also mentioned storage profiles. Can you expand on that a little for our listeners?

Laverick: Storage profiles and VASA work in harmony, because once you have a tool by which you can identify the core storage attributes of the storage … that allows the storage admin to … create these profiles. You can call them like a policy system. By creating a profile, when a new virtual machine is being created, you can use a pull-down list to filter out different types of stores. A simple storage profile might separate the stores that are replicated from the ones that are not replicated, or the stores that support RAID 10, as opposed to the ones that support RAID 5.

The idea is to funnel or guide the person making the new virtual machines down the right route of selecting the right storage. It's one thing to know the attributes, but once those attributes are exposed, what storage profiles allow you to do is then classify your storage by different types.

It's worth saying that there are not just these vendor-defined attributes. [In] VirtualCenter with storage profiles, the admin there can make any definitions they like, called user-defined profiles. They can choose to categorize things by business unit, for example. They can gather all these data stores together and say these particular data stores belong to production, or administration or sales. [That way], the storage is being filtered out by business unit or even by application. They're not limited to just the attributes by the VASA plug-in; they can make their own definitions on the fly if they wish.

SearchVirtualStorage.com: You mentioned that VMware has talked about some things that it might include in its newest release. Can you expand on that?

Laverick: At last year's VMworld there were a couple of sessions that discussed a new way of handling storage, called vVols. I must admit, VMware [doesn't] give out too much information about what this new storage concept is meant to be. But given the close relationship VMware has with storage vendors -- perhaps people listening don’t realize that for every $1 of VMware, practically, a customer spends, they will spend an additional $3 to $4 on storage. Therefore, storage vendors love VMware, and vice versa.

We're moving into a new era where the days of a storage administrator creating LUNs or volumes, and presenting those LUNs or volumes to specific hosts for specific purposes, is now looked upon as being a little bit old-fashioned. I think it's all connected to the new ethos of the cloud. What people want to do is create pools of storage, large pools [that are] terabytes in size, and have them allocated to an entire rack or corridor of servers and allow the application owner (in this case, VMware) to then consume that resource. The idea of this new construct is this thing called vVol.

The other side of this is, historically, virtual machines have been stored together, groups of virtual machines … all on one volume or LUN. That's great from a management perspective -- you don't need a LUN for every virtual machine. But when you do that, you lose some of the granularity that's associated with that. All those virtual machines now share the same replication schedule or the same snapshot schedule. You lose the ability to say, "On this virtual machine, I'd like a replication schedule of every 20 minutes and a snapshot reserve of 30 percent, but with another virtual machine I want something totally different."

Trying to do that with the existing model of LUNs and volumes just won't scale. You can't have a volume and a LUN for every individual virtual machine. As I understand it -- but as I said the information is a bit murky right now -- the vVol is meant to address that: a brand-new storage unit specifically designed with virtualization in mind.

I would think that where storage vendors and VMware lead, you'll find the other virtualization vendors like Microsoft and Citrix, will want to follow and want to build those partnership relationships with the storage vendors so they can take advantage of this new storage construct.

This was first published in June 2012

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