vSphere 5.0: Profile-Driven Storage, what is it good for?

By now most of you heard about this new feature called Profile-Driven Storage that will be introduced with vSphere 5.0, but what is it good for? Some of you, depending on the size of the environment, currently have a nice long operational procedure to deploy virtual machines. The procedure usually contains gathering information about the requirements of the virtual machine’s disks, finding the right datastore to meet these requirements, deploy the virtual machine and occasionally check if the virtual machine’s disks are still placed correctly. This is what Profile-Driven Storage aims to solve.

Profile-Driven Storage, in the vCenter UI referred to as VM Storage Profiles, decrease the amount of administration required to properly deploy virtual machines by allowing for the creation of Profiles. These profiles typically list the requirements of storage and can be linked to a virtual machine. I know it all sounds a bit vague, let me visualize that:

In this scenario a virtual machine requires “Gold Storage”, now lets just assume for now that that means RAID-10 and Replicated. By linking the profile to this virtual machine it is possible to validate if the virtual machine is actually located on the right tier of storage. Now this profile can of course be linked to a virtual machine / virtual disk after it has been provisioned, but even more importantly it can be used during the provisioning of the virtual machine to ensure the user picks a datastore (cluster) which is compatible with the requirements! Just check the following screenshot of what that would look like:

Now you might wonder where this storage tier comes from, this is a VM Storage Profile containing storage capabilities provided by:

  • VASA aka vSphere Storage APIs – Storage Awareness
  • User defined capabilities

User defined capabilities are fairly simple to explain, the profile you create (gold / silver / bronze) will be linked to a User Defined “tag” you define on a datastore. For instance you could tag a datastore as “RAID-10″. When would you do this? Well typically when your storage vendor doesn’t offer a Storage Provider for VASA (yet). That takes us to the second method of selecting storage capabilities for your VM Storage Profile, VASA. VASA is a new “API” which enables you to see the characteristics of a datastore through vCenter. With characteristics I am referring to things like: raid level, de-duplication, replication etc. You know what, my a step-by-step guide makes it clear:

  • Go to VM Storage Profiles
  • Create a VM Storage Profile
  • Provide a Name
  • Select the correct Capabilities
  • Finish the creation
  • Create a new VM and select the correct VM Storage Profile, note that only 1 datastore is compatible
  • After creation you can easily check if it is compliant or not by going to the VMs summary tab

A couple of simple initial steps as you can clearly see, but a huge help when provisioning virtual machines and when validating storage / vm requirements!

vSphere 5.0: Storage DRS introduction

Storage DRS is a brand new feature of vSphere 5.0. It has been one of my focus areas for the last 6 months and probably one of the coolest features of vSphere 5.0. Storage DRS enables you to aggregate datastores in to a single object, called a datastore cluster. This new object is what you will be managing from now on. Storage DRS enables smart placement of virtual machines based on utilized diskspace, latency and LUN performance capabilities. In other words, when you create a new virtual machine you will select a Datastore Cluster instead of a Datastore and Storage DRS will place the virtual machine on one of the datastores in that datastore cluster. This is where the strength lies of Storage DRS, reducing operational effort associated with provisioning of virtual machines…

But that’s not all there is, Storage DRS is a lot more than just initial placement… lets sum the core functionality of Storage DRS up:

  1. Initial Placement
  2. Migration Recommendations (Manual / Fully Automated)
  3. Affinity Rules
  4. Maintenance Mode

These in my opinion are the 4 core pieces of functionality that Storage DRS provides. Initial placement as stated will reduce the amount of operational effort required to provision virtual machines. Storage DRS will figure out which datastore it should be placed on, no need anymore to manually monitor each datastore and figure out which one has the most available diskspace and relative low latency. On top of that SDRS also provides Migration Recommendations if and when thresholds are exceeded, it can generate them (manual mode) or generate and apply them (fully automated mode). These thresholds are utilized disk space(80%) and latency (15ms). This helps preventing bottlenecks in terms of disk space and hot spots in terms of latency.

Affinity Rules and Maintenance Mode are very similar to what DRS offers today. You have the ability to split disks and virtual machines with Affinity Rules, or keep them together. With Maintenance Mode it will be very easy to migrate to new LUNs or to do planned maintenance on a volume, couple of clicks and all VMs will be moved off.

Once again I would like to stress that although the Migration Recommendations (especially in Fully Automated mode) sound really sexy, and it is, it will more than likely be the Initial Placement recommendations where you will benefit the most. More technical information will follow soon here and on frankdenneman.nl

Live Blog: Raising The Bar, Part V

I am live at the Launch event in San Francisco with many other bloggers, journalists and analysts. It is the 12th of July, almost 09:00 PDT and Paul Maritz is about come up on stage to talk about the Cloud Infrastructure launch. This article will be update live during the event as we go.

Paul Maritz is taking the stage… Taking the next step in towards the more automated world.

We need to make infrastructure become something that people can depend on and focus on what is important to their business. Navigating your way forward offering a more dynamic infrastructure that will support your existing applications. Using a more flexible infrastructure, allowing people to take resources and aggregate to larger pools reducing operational costs by automating the use of these resources. More and more use of social media and use of mobile devices to connect anytime anywhere and most importantly securely.

Today we will be talking about  a more efficient infrastructure with exists of three stages IT Production, Business Production and IT as a Service. In 2009, the VI 3 era, 30% of the workloads were virtualized…. in 2010 with vSphere 4 we reached 40% and it is expected that in 2011 we will hit 50% virtualized with the majority on vSphere.

Accelerating and Amplifying business agility with vSphere 5! Not only vSphere 5 but the worlds first Cloud Infrastructure suite! In addition to vSphere 5 today we announce vSphere Site Recovery Manager 5 (Business Continuity), vCloud Director 1.5 (Policy, Reporting, Self-Service), vCenter Operations 1.0.1 (Monitoring and Management), vShield 5 (Security and Edge functionality).

VMware vCloud = Hybrid. Your private cloud experience needs to be similar to public cloud experience. VMware allows this through the vCloud offering and vCloud Service Providers. Trusted vCloud partners like Colt, Bluelock, Singtel, Verizon, NYSE Euronext, Softbank and CSC are some of the enablers for this.

Steve Herrod up on stage… I expect it is about to get more technical

Why do these new products matter and how do they fit together. Accelerating the adoption by increasing scalability. ESX 1.0 capable of 5000 IOps, ESX 2.0 ~ 7000 IOps, VI 3 100.000 IOps, vSphere 4 300.000 IOps and vSphere 5.0 1.000.000 IOps. Besides performance availability is key. Both HA and FT have been enhanced and of course SRM 5.0 has been released. Added to SRM 5.0 is vSphere Replication. vSphere Replication allows you to use the network to replicate between sites and different arrays. It will allow you to replicate more workloads with a lower costs. SRM is about datacenter mobility, not only for an outage but also pro-actively moving datacenters after an acquisition.

What does cloud computing really mean? Being able to order what you need and what without knowing what happens behind the scenes. IT will behind the scenes validate if they meet the consumers requirements. vCloud Director is all about Simple Self-Service. Deploy virtual machines but more importantly create new vApps and offer these in your own “app store”. The IT Cloud of the producer is all about offering agility. Virtualization enables automation in a way unheard in a physical environment.

Typically multiple tiers are offered within a cloud environment. The VMware Cloud Infrastructure enable you to do so. Intelligent Policy based Management is key with vCloud Director 1.5. Linked Clones is a very important feature to provision virtual machines “aggressively” within the system. It allows for fast provisiong and save up to 60% of storage.

Profile-Driven Storage and Storage DRS are part of vSphere 5.0. It enables you to map different arrays in to logical entities by a concept called a “datastore cluster” and link these to a profile. Virtual machines will be tagged with a profile and this allows you to validate compliancy. Storage DRS does for storage what DRS does for compute resources. Storage and Network IO Control ensures each virtual machine receives what it is entitled to.

For the SMB market a brand new shared storage appliance is introduced today: vSphere Storage Appliance 1.0. It takes vanilla servers and use local drives and present it as shared storage. It will bring agility and availability through shared storage to the SMB.

Auto-Deploy, PXE booting your ESXi hypervisor in to memory! It allows to spin-up more hosts within minutes instead of hours. Adding capacity has never been this simple?

vSphere 5 offers comprehensive security and isolation capabilities through vShield 5.0. vShield App 5 allows you to select regulations to protect sensitive data. It also enables you to get additional auditing in place.

The Cloud Infrastructure represents more than a million engineering hours, more than 100 additional capabilities, more than two million QA hours, more than 2000 partner certifications to enable this.

Rick Jackson up next discussing licensing.

Industry has traditionally licensed on physical constraints. It makes it difficult to create a cloud environment. Customers need to be able to upgrade to new hardware without having physical boundaries. No more “Cores per Proc” limits, no more “Physical RAM per host license”… vSphere introducing vRAM entitlement. Virtual RAM is the amount of virtual memory configured for a powered on virtual machine. vSphere 5 used pooled vRAM across the entire environment.

Packaging has been simplified and moving from 6 down to 5 packages. vSphere Advanced has been eliminated, all customers currently using Advanced are entitled to vSphere Enterprise.

Join us at VMworld for more details around the new product releases. 10AM virtual show, be there for more technical in-depth details!

Disk.SchedNumReqOutstanding the story

There has been a lot of discussion in the past around Disk.SchedNumReqOutstanding and what the value should be and how it relates to the Queue Depth. Jason Boche wrote a whole article about when Disk.SchedNumReqOutstanding (DSNRO) is used and when not and I guess I would explain it as follows:

When two or more virtual machines are issuing I/Os to the same datastore Disk.SchedNumReqOutstanding will limit the amount of I/Os that will be issued to the LUN.

So what does that mean? It took me a while before I fully got it, so lets try to explain it with an example. This is basically how the VMware IO scheduler (Start-Time Fair Scheduling aka SFQ) works.

You have set your queue depth for your HBA to 64 and a virtual machine is issuing I/Os to a datastore. As it is just a single VM up to 64 IOs will then end up in the device driver immediately. In most environments however LUNs are shared by many virtual machines and in most cases these virtual machines should be treated equally. When two or more virtual machines issue I/O to the same datastore DSNRO kicks in. However it will only throttle the queue depth when the VMkernel has detected that the threshold of a certain counter is reached. The name of this counter is Disk.SchedQControlVMSwitches and by default it is set to 6, meaning that the VMkernel will need to have detected 6 VM switches when handling I/O before it will throttle the queue down to the value of Disk.SchedNumReqOutstanding, by default 32. (VM Switches means that it will need to detect 6 times that the selected I/O is not coming from the same VM as the previous I/O.)

The reason the throttling happens is because the VMkernel cannot control the order of the I/Os that have been issued to the driver. Just imagine you have a VM A issuing a lot of I/Os and another, VM B, issuing just a few I/Os. VM A would end up using most of the full queue depth all the time. Every time VM B issues an I/O it will be picked quickly by the VMkernel scheduler (which is a different topic) and sent to the driver as soon as another one completes from there, but it will still get behind the 64 I/Os already in the driver, which will add significantly to it’s I/O latency. By limiting the amount of outstanding requests we will allow the VMkernel to schedule VM B’s I/O sooner in the I/O stream from VM A and thus we reduce the latency penalty for VM B.

Now that brings us to the second part of all statements out there, should we really set Disk.SchedNumReqOutstanding to the same value as your queue depth? Well in the case you want your I/Os processed as quickly as possible without any fairness you probably should. But if you have mixed workloads on a single datastore, and wouldn’t want virtual machines to incur excessive latency just because a single virtual machine issues a lot if I/Os, you probably shouldn’t.

Is that it? No not really, there are several questions that remain unanswered.

  • What about sequential I/O in the case of Disk.SchedNumReqOutstanding?
  • How does the VMkernel know when to stop using Disk.SchedNumReqOutstanding?

Lets tackle the sequential I/O question first. The VMkernel will allow by default to issue up to 8 sequential commands (controlled by Disk.SchedQuantum) from a VM in a row even when it would normally seem more fair to take an I/O from another VM. This is done in order not to destroy the sequential-ness of VM workloads because I/Os that happen to sectors nearby the previous I/O are handled by an order of magnitude (10x is not unusual when excluding cache effects or when caches are small compared to the disk size) faster than an I/O to sectors far away. But what is considered to be sequential? Well if the next I/O is less than 2000 sectors away from the current the I/O it is considered to be sequential (controlled by Disk.SectorMaxDiff).

Now if for whatever reason one of the VMs becomes idle you would more than likely prefer your active VM to be able to use the full queue depth again. This is what Disk.SchedQControlSeqReqs is for. By default Disk.SchedQControlSeqReqs is set to 128, meaning that when a VM has been able to issue 128 commands without any switches Disk.SchedQControlVMSwitches will be reset to 0 again and the active VM can use the full queue depth of 64 again. With our example above in mind, the idea is that if VM B is issuing very rare IOs (less than 1 in every 128 from another VM) then we still let VM B pay the high penalty on latency because presumably it is not disk bound anyway.

To conclude, now that the coin has finally dropped on Disk.SchedNumReqOutstanding I strongly feel that the advanced settings should not be changed unless specifically requested by VMware GSS. Changing these values can impact fairness within your environment and could lead to unexpected behavior from a performance perspective.

I would like to thank Thor for all the help he provided.