Tag Archives: vasa

Is VAAI beneficial with Virtual Storage Appliance (VSA) based solutions ?

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I saw a tweet recently (below) which inspired me to write this post as there is still a clear misunderstanding of the benefits VAAI provides (even with Virtual Storage Appliances).

vaaionvsatweet2

I have removed the identity of the individual who wrote the tweet and the people who retweeted this as the goal of this post is solely to correct what I believe is mis-information.

My interpretation of the tweet was (and remains) if a solution uses a Virtual Storage Appliance (VSA) which resides on the ESXi host then VAAI is not providing any benefits.

My opinion on this topic is:

Compared to a traditional centralised NAS (such as a Netapp or EMC Isilon) providing NFS storage with VAAI-NAS support, a Nutanix or VSA solution has exactly the same benefits from VAAI!

My 1st reply to the tweet was:

vaaionvsatweetconvojoshreply2

The test I was referring to with Netapp OnTap Edge can be found here which was posted in Jan 2013, well prior to my joining Nutanix when I was working for IBM where I had been evangelising VAAI/VCAI based solutions for a long time as VAAI/VCAI provides significant value to VMware customers.

The following shows the persons initial reply to my tweet.

vaaionvsatweetconvo32

I responded with the below mentioning I will do a blog which is what you’re reading now.

I went onto provide some brief replies as shown below.

repliesdetail

The main comments from this persons tweets I would summarize (rightly or wrongly) below:

  • VAAI is designed only to offload functions externally (or off the ESXi host)
  • He/She had not seen any proof of performance advantages from VAAI on VSAs
  • Its broken logic to use VAAI with a VSA

Firstly, I would like comment on VAAI being designed to offload functions externally (or off the ESXi host). I don’t disagree VAAI has some functions designed to offload to the (centralised) array but VAAI also has numerous functions which are designed to bring other efficiencies to a vSphere environment.

An example of a feature designed to offload to a central array is the “XCOPY” primitive.

A simple example of what “XCOPY” or Extended Copy provides is offloading a Storage vMotion on block based storage (i.e.: VMFS over iSCSI,FC,FCoE not NFS) to the array so the ESXi host does not have to process the data movement.

This VAAI primitive would likely be of little benefit in a VSA environment where the storage is presented is block based and Storage DRS for example was used. The data movement would be offloaded from ESXi to the VSA running on ESXi and host would still be burdened with the SvMotion.

However XCOPY is only one of the many primitives of VAAI, and VAAI does alot more than just offload Storage vMotions.

For the purpose of this post, I will be discussing VAAI with Nutanix whos Software defined storage solution runs in a VM on every ESXi host in a Nutanix cluster.
Note: This information is also relevant to other VSAs which support VAAI-NAS.

So what benefit does VAAI provide to Nutanix or a VSA solution running NFS?

Nutanix deploys by default with NFS and supports the VAAI-NAS primitives which are:

  • Full File Clone
  • Fast File Clone
  • Reserve Space
  • Extended Statistics

Note: XCOPY is not supported on NFS, importantly and specifically speaking for Nutanix it is not required as SvMotion will be rarely if ever used with Nutanix solutions.

See my post “Storage DRS and Nutanix – To use, or not to use, that is the question?” for more details on why SvMotion is rarely needed when using Nutanix.

For more details of VAAI primitives, Cormac Hogan (@CormacJHogan) wrote an excellent post which can be found here.

Now here is an example of a significant performance benefits of VAAI with Nutanix.

Lets look at Clone of a VM on a Nutanix platform, the VMs details are below.admin01vm

The VM I have used for this test resides on a datastore called “Management” (as per the above image) which presented via NFS and has VAAI (Hardware Acceleration) enabled as shown below.datastore

Now if I do a simple clone of a VM (as shown below) if the VM is turned on, VAAI-NAS is bypassed as the “Fast File Clone” primitive only works on VMs which are powered off.

clone

So a simple way to test the performance benefits of VAAI on any platform (including Hyper-converged such as Nutanix, a Virtual Storage Appliance (VSA) such as Netapp Ontap Edge or traditional centralised SAN or NAS) is to clone a VM while powered on then shut-down the VM and clone it again.

I performed this test and the first clone with the VM powered on started at 1:17:23 PM and finished at 1:26:12 PM, so a total of 8 mins 49 seconds.

Next I shut down the VM and repeated the clone operation.cloneresults

As we can see in the above screen capture from the 2nd clone started at 1:26:49 PM and finished at 1:26:54 PM, so a total of 5 seconds.

The reason for the huge difference in the speed of the two clones is because VAAI-NAS “Fast File Clone” primitive offloaded the 2nd clone to the Nutanix platform (which runs as a VM on the ESXi host) which has intelligently cloned the VM (using metadata resulting in almost zero data creation) as opposed to 1st clone where VAAI-NAS was not used which resulted in the hypervisor and storage solution having to read 11.18GB of data (being the source VM – Admin01) and write a full copy of the same data resulting in effectively >22GB of data movement in the environment.

Now from a capacity savings perspective, a simple way to demonstrate the capacity savings of VAAI on any platform is to clone a VM multiple times and compare the before and after datastore statistics.

Before I performed this test I captured a baseline of the Management datastore as shown below.

BeforeCloningCapacityVMcount

The above highlighted areas show:

  • Virtual Machines and Templates as 83
  • Capacity 8.49TB
  • Provisioned Space 7.09TB
  • Free Space 7.01TB

I then cloned the Admin01 VM a total of 7 times.clone7vmsrecenttasks

Immediately following the last clone completing I took the below screen shot of the Management datastores statistics.

AfterCloningCapacityVMcount

The above highlighted areas in the updated datastore summary show:

  • Virtual Machines and Templates INCREASED by 7 to 90 (as I cloned 7 VMs)
  • Capacity remained the same at 8.49TB
  • Provisioned Space INCREASED to 7.29TB as we cloned 7 x ~40Gb VMs (Total of ~280GB)
  • Free Space REMAINED THE SAME at 7.01TB due to VAAI-NAS Fast File Clone primitive working with the Nutanix Distributed File System.

So VAAI-NAS allowed a VM of ~11GB of used storage (~40GB provisioned) to be cloned without using any significant additional disk space and the clones were each done in between 5 and 7 seconds each.

So some of the benefits VAAI-NAS provides to Nutanix (which some people would term as a VSA type solution) include:

  • Near instant VM cloning via vSphere Client/s (as shown above)
  • Near instant Horizon View Linked Clone deployments (VCAI) – Similar to example shown.
  • Near instant vCloud Director clones (via FAST Provisioning) – Similar to example shown.
  • Major capacity savings by using Intelligent cloning rather than Full Clones (As shown above)
  • Lower CPU overhead for both ESXi hosts AND Nutanix Controller VM (CVM)
  • Ability to create EagerZeroThick VMDKs on NFS (e.g.: To support Fault Tolerance & clustered workloads such as Oracle RAC)
  • Enhanced ability to get statistics on file sizes , capacity usage etc on NFS

In Summary:

Overall I would say that VMware have developed an excellent API in VAAI and Nutanix along with VSA providers having support for VAAI provides major advantages and value to our joint customers with VMware.

It would be broken logic NOT to leverage the advantages of VAAI regardless of storage type (VSA, Nutanix or traditional centralized SAN/NAS) and for the vast majority of vSphere deployments, any storage solution not supporting (or having issues/bugs with) VAAI will have significant downsides.

I am looking forward to ongoing developments from VMware such as vVols and VASA 2.0 to continue to enhance storage of vSphere solutions in the future.

I hope customers and architects now have the correct information to make the most effective design and purchasing recommendations to meet/exceed customer requirements.

Melbourne VMUG Feb 7th 2013 – Optimizing VMware vSphere , vCloud and VDI Environments with Intelligent Storage

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Last month I presented a Community Session at the Melbourne VMUG

“Optimizing VMware vSphere , vCloud and Desktop Environments with Intelligent Storage”

For those who are interested, you can watch the recorded session here.

A special Thanks to Craig Waters (@cswaters1) Melbourne MVUG leader for organizing the Melbourne VMUG and recording/encoding this session for the VMware community.

Example Architectural Decision – Storage DRS Configuration for VMFS Datastores in a vCloud Environment

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Problem Statement

In a production , self service vCloud Director environment, What is the most suitable Storage DRS configuration to improve storage utilization , performance, as well as reduce administrative effort for BAU staff?

Requirements

1. Make the most efficient use of the available storage capacity
2. Maintain consistent level of storage performance
3. Reduce the risk and overhead of capacity management
4. Reduce the risk of a unintentional or otherwise DoS event caused by self service

Assumptions

1. vSphere 5.0 or later
2. VMFS 5 Datastores which are Thick Provisioned
3. Deduplication is not in use
4. VAAI is supported by the array and enabled across the vSphere environment
5. All datastores in each respective Datastore clusters reside on the same RAID type with similar spindle types and count
6. All datastores are presented to all hosts within the cluster
7. Array level snapshots are not in use
8. IBM SVC Storage is being used
9. vCloud Director 5.1 or later
10. Storage I/O Control is enabled at set to 30ms

Constraints

1. IBM SVC storage does not currently support VASA (VMware API for Storage Awareness)

Motivation

1. Ensure production storage performance is not negatively impacted
2. Minimize the vSphere administrators workload where possible

Architectural Decision

Set the DRS automation setting to “Fully Automated”

  • Set “Utilized Space” threshold to 80%
  • Set “I/O latency” to 15ms
  • I/O Metric Inclusion – Enabled

Advanced Options

  • No recommendations until utilization difference between source and destination is: 10%
  • Evaluate I/O load every 8 Hours
  • I/O Imbalance threshold  4

Justification

1. Setting Storage DRS to “Fully Automated”  ensures that the administrator does not need to be concerned with initial placement of virtual machines as this will be dynamically and intelligently determined and executed

2. “XCOPY” is fully supported for Block based storage, as such, any Storage vMotion activity is offloaded to the array therefore removing the I/O overhead on the compute and storage fabric.

3. Where a significant I/O imbalance is detected by SDRS, the vSphere administrator is not required to take any action, Storage DRS can identify and remediate issues which fall outside parameters (which are determined by the VMware Architect) automatically. This improves the efficiency of the environment, and reduces the involvement of BAU.

4. SDRS provides valuable “initial placement” for new virtual machines which will help avoid a situation where datastores are unevenly balanced from a capacity perspective in the first place, therefore reducing the chance of virtual machines requiring migration.

5. Setting the “No recommendations until utilization difference between source and destination is” to 20% ensures that SDRS does not move virtual machines around where significant benefit is not realized  This prevents unnecessary Storage vMotion activity on the disk system, although this is offloaded from the host to the array, the I/O still may impact production performance for workloads on the same disk system.

6. Setting the “I/O Imbalance threshold (5 Aggressive / Conservative 1 ) to “4” (2nd most aggressive)  ensures that I/O imbalance should be addressed before significant imbalance is experienced by the end users. This level of “ aggressiveness” is acceptable as the Storage vMotion can be offloaded (via VAAI “XCOPY” primitive  and has almost zero impact on the host.  Setting this to “5” may result in minor I/O imbalances being corrected, at the cost of a Storage vMotion and as a result the impact of the more frequent Storage vMotion activity may negate the benefit of the I/O balancing.

7. Storage DRS will address I/O imbalance across the datastore cluster if the latency meets or exceeds the set value of 15ms (the default) and in the event of latency increasing during peak times to >=30ms , Storage I/O Control will ensure fair acess to the storage.

Alternatives

1. Use “No Automation (Manual Mode)”
2. Not use Storage DRS

Implications

1. When selecting datastores for the datastore cluster, having VASA enabled allows the “System Capability” column to be populated in the “New Datastore Cluster” wizard to ensure suitable datastores of similar performance, RAID type and features are grouped together. VASA is currently NOT supported by SVC, as such the datastore naming convension needs to accurately reflect the capabilities of the LUN/s to ensure suitable datastores are grouped together.

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