Stepping out of a subway car is an entirely different matter when it's moving!

Mobility of virtual machines is a sticky wicket. As open systems infrastructure becomes increasingly virtualized, administrators and managers wish to use the technology to balance workload, ease migration, and provide better availability. Although technology is improving, actually moving virtual machines is not always a piece of cake. Let’s lay down a baseline of information so we may begin a discussion on the true nature of virtual machine mobility.

Mobility of What?

Let us consider first the question of what exactly is being moved. Systems administrators often focus on “the machine”, which encompasses the operating system and configured state of the virtual machine itself. But the true “mass” of the system is its stored data. Hypervisor vendors have come up with different techniques of moving these two essential elements, reflecting the unique characteristics of each.

• The virtual machine is an instance of an operating system along with its state and configuration. Mobility of virtual machines requires all of this to be preserved, along with any I/O channels. Live migration of virtual machine requires that any active network sessions be maintained, along with RAM content, registers and buffers, and so many other elements.
• The virtual machine image (commonly referred to as “storage”) is the static content addressed by a virtual machine. Typically a VMDK or similar virtual disc image, it must be accessible to the virtual machine at all times. Live migration of a virtual machine image is tricky, but perhaps not quite as complex as live migration of a running operating system.

VMware, Microsoft, and others recognize these 2 distinct elements to be migrated, and have come up with a variety of complementary technologies for each:

• vMotion is VMware’s virtual machine migration solution, and has continually evolved with each iteration of the hypervisor. DRS leverages vMotion to automate mobility. VMware has also created Storage vMotion and Storage DRS as complements to handle mobility of virtual machine images.
• Microsoft Hyper-V Live Migration is conceptually similar to vMotion, though newer and less full-featured. With Hyper-V 3.0, Microsoft will introduce Storage Live Migration as a complementary technology akin to Storage vMotion. Most other virtual machine managers also support some form of live migration, though live migration of storage is less common.

Mobility in What State?

One of the key benefits of virtual machine technology is the ability to “run anywhere” on dissimilar hardware. From the very beginning, hypervisors have provided the ability to create a universal virtual machine image that would run on a variety of supported platforms.

This leads to one of the key values of server virtualization in the data center: Disaster recovery. The ability to take a virtual machine image and system state and bring it online after a disaster is a true revolution for open systems IT. The benefits of the single usage of server virtualization technology easily justify the investment to many businesses.

But this sort of “cold” migration seems passé when compared to the live or “hot” migration possible with technologies like VMware vMotion. Live migration is much more difficult, since active client sessions must be preserved in activity must not be greatly interrupted.

This is the second great question that must be asked when considering virtual machine mobility: In what state will the virtual machine be moved? Will it be a cold, powered down image of the system? A suspended or paused operating system image? Or a full, running machine?

Mobility to Where?

Once we have decided whether we are discussing virtual machine migration or movement of storage resources, we must consider the scope of the movement. The ability to move a virtual machine from one member of the cluster to another has now become fairly common. But what about systems that are not related in a cluster? Or that are spread over great distances?

• The nice thing about clusters is that they share resources before and after a virtual machine is moved. It is practical to move the running virtual machine, its storage, or both independently and to expect that performance will not dramatically suffer as a result. The cluster can also preserve network connections, and even I/O state, without much impact on clients or other external elements.
• It is a bit more difficult to move systems within a data center, since one must maintain the I/O connections that might be interrupted. It is fairly trivial to configure an IP network and storage array to allow multiple machines to access the same iSCSI or NFS storage resources. It is a little more difficult to configure Fibre Channel (and, by extension, FCoE) SAN’s to handle this sort of dynamic movement, but it is not impossible. Although moving a running machine from one network port to another could cause client access to be interrupted, technologies like VXLAN allow these sessions to continue, and improved network switching technology should reduce performance impact.
• Moving the machine to a different data center is another matter entirely. Stretching a layer-2 Ethernet LAN or Fibre Channel SAN across a metro or greater distance, while possible, will always be problematic. IP routing is flexible, but it takes time for changes to propagate when live machines are moved. And it is difficult to keep storage in sync over long distances due to the amount of time it takes for information to transit. Again, all of these challenges are being addressed in various ways, but they’re still hard!

Stephen’s Stance

Moving cold virtual machine images from system to system, or even across great distances, is one of the main selling points of server virtualization. But it becomes much more difficult to manage movement of virtual machines that are still running, especially outside cluster or across WAN links. When talking about virtual machine mobility, it is important to consider what is being moved, the state it is in, and where it is going.

Note: This discussion is part of “Building Virtual Infrastructure”, my new seminar series with Truth in IT.

© sfoskett for Stephen Foskett, Pack Rat, 2012. | Virtual Machine Mobility: Of What, and to Where and in What State?
This post was categorized as Enterprise storage, Features, Gestalt IT, Virtual Storage. Each of my categories has its own feed if you'd like to filter out or focus on posts like this.

VASA allows a "provider" application to tag vSphere storage with a "capabilities" string

The list of VMware storage integration features in vSphere is growing at a rapid pace. From backup to enterprise array offload, VMware is staking their claim. But information about one new storage feature in vSphere 5 has been scarce: The true nature of the Storage API for Storage Awareness (VASA) is only just beginning to be revealed.

VASA: Born of Necessity

vSphere has some amazing automated storage mobility features. The ease of moving data between LUNs and even arrays with Storage vMotion is a revelation to those of us unlucky enough to have used manual migration methods in the past. And VMware has automated this with the new Distributed Resource Scheduler (DRS) capability, allowing vSphere to make its own decisions about data placement.

But this kind of dynamic movement can hurt as well as help. What if an administrator moves a VMDK from high-performance to low-performance storage? Server responsiveness would suffer, perhaps even resulting in an application outage. And how could Storage DRS avoid doing the same thing?

VMware realized they needed some mechanism that could “tag” a storage resource with its capabilities. This is the real reason for their creation of Profile-Driven Storage and VASA.

VASA Does One Thing

In vSphere 5, VASA is incredible simple: It is a basic protocol for vSphere to request a “capabilities” string regarding a LUN or NFS share from a “provider”. The content of this response, and indeed the form that this provider will take, is left up to the individual storage vendors.

VASA Providers can take many forms. Dell is reportedly developing a vCenter plugin to report capabilities. EMC and NetApp will use a software application that runs on a virtual or physical server. In all cases, the software uses a proprietary call to the storage array, in effect relaying and translating the VMware request.

The VASA “Capabilities” string is undefined as well. Most vendors use a list of technical attributes as their response string, and each has adopted their own strategy about how to present information:

• Dell’s EqualLogic returns a comma-separated list like “RAID, SSD, REPLICATED”
• NetApp’s provider uses semicolons, as in “Dedupe; Replication”
• HP’s is very detailed, with a schema specifying Drive Type, RAID Type, Provisioning Type, VV Type, and Remotecopy
• EMC appears to have a standardized set of much-shorter tags, like “Performance”, “Multi-Tier”, “Capacity” and such

These are passed through to vCenter, where an administrator can decide how to interpret them.

VASA Today and Tomorrow

In its simplest form, VASA capabilities tags enable both manual and automatic storage placement features to respect tiered storage policies. This is important to maintain proper system performance and availability. In the future, I expect more advanced VASA providers, perhaps even integration of the providers into vCenter plugins. I also look forward to a standard capabilities tagging schema and smarter handling of returned tags. Right now, for example, EMC’s Clariion and Symmetrix lines both tag LUNs as “Performance”, but these are obviously not equivalent.

© sfoskett for Stephen Foskett, Pack Rat, 2011. | What is VMware VASA? Not Much (Yet)
This post was categorized as Enterprise storage, Features, Virtual Storage. Each of my categories has its own feed if you'd like to filter out or focus on posts like this.

For more information on earlier updates, see my articles:

• Storage Fixes in VMware ESX Server 3.5 Update 2
• Storage Changes in VMware ESX 3.5 Update 3
• Storage Changes in VMware ESX 3.5 Update 4
  
• Storage Changes in the VMware vSphere 4 Family

One first step is VMware’s whitepaper, “What’s New in VMware vSphere 5.0 – Storage“.

Licensing and Availability of Features

VMware has once again changed the licensing and pricing model, throwing the Internet into a tizzy:

• “Advanced” has been eliminated, moving up to “Enterprise”
• Pooled vRAM entitlements work across the entire vCenter environment
• New features like Policy-Driven Storage and Storage DRS (along with SIOC) are exclusive to “Enterprise Plus” licenses
• VAAI, PSP multipathing, and Storage vMotion are only found in “Enterprise”
• Thin Provisioning and VADP are available regardless of edition

VMware mucked with vSphere licensing again...

Major New vSphere 5 Storage Features

Storage DRS

Storage DRS is the world’s worst-kept secret, with everyone and his brother talking about it for over a year. Like the existing VM DRS capability, Storage DRS creates resource clusters and automatically moves VMs between them. Storage DRS uses utilization and performance metrics to make the call, and has three modes of operation. It sounds awesome, but it’s an Enterprise Plus-only feature.

Storage APIs – Storage Awareness (VASA)

There’s not much information presently, but a VAAI companion is introduced in vSphere 5: The vSphere Storage APIs for Storage Awareness (VASA) is a communication mechanism for vCenter to detect array capabilities like RAID Level, Thin Provisioning State, Replication State, etc. This will come in handy for all the other features in vSphere 5, especially policy-driven storage!

Policy-Driven Storage

Another new Enterprise Plus feature is Policy-Driven Storage. This allows storage tiers to be defined in vCenter based on SLA, performance, and other metrics which are used during provisioning, cloning, Storage vMotion, and Storage DRS. It leverages VASA for metrics and characterization and supports all arrays in the HCL, regardless of whether they’re NFS, iSCSI, or FC. It includes easy compliance status reporting in vCenter as well.

FCoE Software Initiator

Those of us “in the know” about storage expected VMware to add software FCoE support, so it’s no surprise that they did. This dramatically expands the potential FCoE footprint from just the few CNAs already supported in vSphere 4. It appears to be based on Intel’s OpenFCoE, since it shows up as “Intel Corporation FCoE Adapter” in the GUI!

vSphere Storage Appliance (VSA)

VMware enters the virtual storage appliance (VSA) market with their own offering, the vSphere Storage Appliance (also called VSA). Aimed primarily at the SMB market, it’s actually fairly clever, replicating storage between two or three nodes in a cluster for high availability and using NFS for access rather than iSCSI. And unlike the Celerra UBER that so many techies loved, the VMware VSA is ready for production use!

Existing Storage Features Enhanced in vSphere 5

VMFS 5

VMFS has been improved for scalability and efficiency, but the 2 TB limit on VMDKs remains (except for physical RDM). Only storage geeks like me need to worry about the specifics, but suffice to say that VMFS 5 requires less tuning and worrying and ought to scale and perform better thanks to increased maximums and leveraging the Atomic Test and Set (ATS) technology also used in VAAI. For newly-created volumes, there’s no more block size tuning, and alignment issues are addressed.

Storage APIs – Array Integration (VAAI 2)

See also VMware VAAI Storage Array Support in Plain English

VAAI has been revved, bringing back Thin Provisioning Stun (the AWOL “fourth primitive”) and adding NFS support.

There are now five block primitives for VAAI, depending on if you count thin space reclaim. This is really more of a bug fix than anything, since most folks assumed that the existing thin support already reclaimed deleted VMs and vMotioned VMDKs. I’m more interested in the addition of SCSI UNMAP in addition to WRITE_SAME! There’s also some additional T10 support, though I’m not clear on what it is or where it works.

We’ve also got VAAI for NFS environments now. NAS had sweet thin provisioning support even before block datastores, but the new Reserve Space command adds thick provisioning if that’s what you like. We’ve also got Full File Clone, which is like Full Copy for NFS but doesn’t work with Storage vMotion. And there’s some Extended Stats API to bring in more detail on file status. I also hear there’s an API for Native Snapshot Support, but it’s not widely discussed. Finally, note that NFS plugins come from vendors, not VMware as is the case for block VAAI.

Storage I/O Control

SIOC is enhanced for use in Storage DRS environments, becoming aware of the new datastore clusters. It also gets NFS support, and presumably uses VASA for metrics. But it’s still only available with Enterprise Plus licenses.

iSCSI Initiator GUI

The solid vSphere iSCSI initiator gets a friendly GUI for configuration. I like friendly iSCSI GUIs – just ask Microsoft!

Storage vMotion

The mechanism behind Storage vMotion has changed for a third time in as many releases, this time using “Mirror Mode” to mirror writes to in-progress vMotions. It also now supports migration of vSphere snapshots and Linked Clones. This can be offloaded for VAAI block, but not NFS.

vSphere Replication

New in vCenter Site Recovery Manager 5.0 is software-based replication. Although not technically a vSphere 5 feature, this is a major new storage feature in the VMware world. It allows any-to-any software-based storage replication for disaster recovery.

Stephen’s Stance

Once again, VMware added a ton of new storage enhancements to vSphere. With storage rapidly becoming the limiting factor in scalability and performance of virtual machine environments, this is no surprise. Also not surprising is the fact that major features like Policy-Driven Storage and Storage DRS (along with SIOC) are exclusive to “Enterprise Plus” licenses. I can’t blame VMware for making a buck, but it would be nice if more capabilities were available to the small shops!

I’ll be writing on all these features in detail shortly. Watch this space!

© sfoskett for Stephen Foskett, Pack Rat, 2011. | Storage Changes in VMware vSphere 5
This post was categorized as Enterprise storage, Features, Virtual Storage. Each of my categories has its own feed if you'd like to filter out or focus on posts like this.

For more information on earlier updates, see my articles:

• Storage Fixes in VMware ESX Server 3.5 Update 2
• Storage Changes in VMware ESX 3.5 Update 3
• Storage Changes in VMware ESX 3.5 Update 4
  

One first step is VMware’s whitepaper, “What’s New in VMware vSphere 4: Storage“.

Licensing and Availability of Features

The most important change at a glance is in the licensing model for VMware.

• A new low-end “standard” level includes all of the components a small business might need, including thin provisioning of storage, at a very attractive price.
• The “advanced” level includes advances in the area of data protection.
• At the “enterprise” level, live migration of storage is enabled.
• Top of the heap is “enterprise plus”, which enables the intriguing plug-in third-party multipathing support previously rumored.
• Enterprise customers with current support will get vStorage thin provisioning and data protection when they upgrade.

Each step up the licensing ladder enables important new storage features (source: VMware)

Thin Provisioning

One of the most widespread storage features is native thin provisioning. VMware ESX 4 will allocate storage in 1 MB chunks as capacity is used. This isn’t really completely new – similar support was enabled by default for virtual disks on NFS in VI 3, and thin provisioning could be enabled on the command line for block-based storage as well. It was also present in VMware’s desktop products, including my own copy of Fusion. And ESX allows thick-to-thin conversion during Storage VMotion.

The difference with vSphere 4 is that thin provisioning is fully supported and integrated into every version of ESX. Although many storage arrays now also offer thin storage, the addition of native, integrated thin provisioning right in ESX is huge. This alone will be a major capacity (and thus, cost) savings feature! VMware claims 50% storage savings in their lab tests.

Dynamic Expansion of VMFS Volumes

VMFS volumes can now grow (and, in some cases, shrink) online without resorting to spanning to a new LUN. Under vSphere 4, VMFS volumes can grow to take advantage of expanded LUNs (up to 2 TB per LUN). The old method still works as well, and multi-LUN spanned VMFS volumes can grow when any of their LUNs is expanded.

Enhanced Storage VMotion

Like thin provisioning, Storage VMotion has been elevated to first-class status, supported just about everywhere you’d want it. It’s in all the likely spots within vCenter.

Storage VMotion gives serious storage flexibility now, enabling (almost) any-to-any migration of VMFS volumes: Pick up a Fibre Channel, iSCSI, or NFS disk image and move it to another datastore running any of those protocols to convert live. And you can do thick-to-thin provisioning at the same time.

Under the hood, the whole infrastructure has been revised. Storage VMotion leverages VMware’s change block tracking instead of disk snapshots now, speeding up the migration process and reducing the (formerly excessive) memory and CPU requirements of Storage VMotion in 3.5. This is the same technology leveraged by vSphere’s High Availability features, by the way.

Pluggable Storage Architecture (PSA)

Only “Enterprise Plus” licensees will get to use it, but the vSphere family also sports a new pluggable storage architecture (PSA) which will initially be leveraged to deliver vendor-specific multipath support. Note that the native multipath support in vSphere continues to be a basic round-robin or fail-over system – it will not dynamically load balance I/O across multiple paths or make more intelligent decisions about which paths to use.

vSphere 4's Pluggable Storage Architecture allows third-party developers to replace ESX's storage I/O stack (source: VMware)

As you may gather from this VMware illustration (but would probably miss since it’s not all that comprehensible), there are two classes of third-party plug-ins:

1. Basic path-selection plugins (PSPs) will merely optimize the choice of which path to use, ideal for active/passive type arrays
2. Full storage array type plugins (SATPs) will allow load balancing across multiple paths in addition to path selection for active/active arrays

EMC also announced PowerPath/VE for vSphere, integrating their popular multi-platform path management software directly into ESX. It’s not clear at this point whether PowerPath will require an Enterprise Plus license (or if it will come with one) or if it will work with all editions, but I’m sure that will be clarified soon. My EMC contacts do tell me that PowerPath/VE is licensed on a per-socket basis (like VMware of yore) and that EMC sales reps have some room to get creative on licensing.

iSCSI Software Initiator Enhancements

It’s harder to claim it as a new feature, but the iSCSI software initiator has also been tweaked and tuned to use less CPU time and deliver better throughput. The iSCSI configuration process has also been smoothed out so one no longer needs to have a live Service Console connection in order to communicate with an iSCSI target. And changes made in the general tab are now global, so they’ll propagate down to each target. Bi-directional CHAP is also added, so the target can now be authenticated in addition to the initiator.

vSphere also includes a paravirtualized iSCSI driver (PVSCSI) which works like vmxnet to present a higher-performance iSCSI adapter within certain supported guest OSes.

More information on multipathing iSCSI can be found at Yellow Bricks and in Chad Sakac’s mega-post on the topic.

High-Performance I/O

vSphere really pours on the I/O power. They claim a 3x increase, to “over 300,000 I/O operations per second”, but mentioned in the launch that they’ve gotten to 400,000 in some workloads. This is really amazing, and if it’s true in real-world use means that VMware ESX can now host just about any application you can think of.

It’s funny, but just a few weeks before the announcement VMware’s Chief Data Center architect, Scott Davis, told me at Storage Networking World that vSphere would double I/O performance. I thought this was a bold statement at the time, but VMware went further in their official documents, claiming 3x improvement. Now we have an on-stage admission that it could be up to 4x! This is serious stuff, folks: Can VMware really do 400,000 IOPS?

One question is whether these IOPS improvements require the new VMDirectPath I/O for Storage, which binds a physical Fibre Channel HBA to a single guest OS, or if they’re generalized across all systems.

vCenter Improvements

vCenter now includes more storage information:

• Each VM and ESX in the inventory has a tab showing storage information and allowing users to set alarms on storage use – setting capacity alarms becomes extremely important when thin provisioning is used!
• vCenter inventory has a view showing datastore details
• There’s also a nice storage topology map

Data Protection APIs (Updated)

VMware also enhanced the APIs for consolidated backup (VCB) into “vStorage Data Protection”. Available only with Advanced or Enterprise licenses, these APIs allow enterprise backup vendors to develop specific integration with VMware without VCB in the middle.  All versions of ESX include this vStorage API and boast VCB support. Standard and Essentials licenses do not include vCenter Data Recovery, a standalone disk-to-disk backup capability for virtual machines.

Conclusion

vSphere is loaded with storage improvements, though many seem like incremental updates rather than new features. Admins will welcome thin provisioning support, and the full integration of Storage VMotion is certainly welcome, but I think the changes to vCenter will be most noticeable. I’ll be looking into EMC’s PowerPath/VE and the amazing I/O improvements as we move forward and learn more about the next ESX!

Duncan Epping posted much more vSphere Linkage on his Yellow Bricks blog if you’re interested in non-storage features. I also suggest reading Chris Evans’ outline of vSphere storage changes.

© sfoskett for Stephen Foskett, Pack Rat, 2009. | Storage Changes in the VMware vSphere 4 Family
This post was categorized as Enterprise storage, Gestalt IT, Virtual Storage. Each of my categories has its own feed if you'd like to filter out or focus on posts like this.

1. Support for Volume Shadow Copy Service (VSS) for filesystems Windows Server 2003 and Windows Server 2008 guests.  This means VMware services like VCB and SRM can now signal Windows Server to quiesce filesystems before creating a clone or snapshot and is a major addition!
2. Windows Server 2003 guests also get application quiescing, where supported.
3. You can now extend a live, running VMFS volume as storage is added, just like Windows Vista and 2008 guests could already do with raw device mode (RDM).  Note that this only works for flat disks with no persistent snapshots open.

A few items are now officially supported, too:

1. Support for Storage VMotion between and among Fibre Channel and iSCSI datastores is here, and in Update 1.
2. iSCSI over 10 gigabit Ethernet (10 GbE) is now supported allegedly, though the I/O Compatibility Guide still says “Gigabit only”.  Of course, it already worked, but it’s nice to have official support just the same…  Bring on the datacenter Ethernet!  They’ll support this in Update 1 too.
3. And NFS over 10 GbE is supported, too!

1. They supposedly added support for 8 gigabit Fibre Channel (8 Gb FC) HBAs, but I don’t see it in the I/O Compatibility Guide. The Emulex LP12000/LP12002 are noted as 4 Gb only, the QLogic QLE2560/QLE2562 aren’t listed, the HP 81/82 series isn’t there either.  Update:  QLogic and Emulex HBAs are supported after all!
2. Support for more Serial-Attached SCSI (SAS), including Dell SAS 5/E, LSI 1078, Sun SG‐XPCIESAS‐R‐EXT‐Z, and HP SC08GE is listed in the Stotage Compatibility Guide.
3. CIM system health monitoring of some QLogic and Emulex HBAs is new too.

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See also:

• Scott Lowe’s (as always) excellent overview
• VM /ETC’s colorful post
• Excellent coverage at Yellow Bricks

© sfoskett for Stephen Foskett, Pack Rat, 2008. | Storage Fixes in VMware ESX Server 3.5 Update 2
This post was categorized as Enterprise storage, Virtual Storage. Each of my categories has its own feed if you'd like to filter out or focus on posts like this.