Monday, May 11, 2020

Undocumented HA Advanced Option - das.restartVmsWithoutResourceChecks

Some time ago, a colleague of mine (@stan_jurena) was challenged by one VMware customer who experienced APD (All Path Down) storage situation in the whole HA Cluster and he expected that VMs will be killed by VMware Hypervisor (ESXi) because of HA Cluster APD response setting "Power off and restart VMs - Aggressive restart policy". To be honest, I had the same expectation. However, after the discussion with VMware engineering, we have been told, that the primary role of HA Cluster is to keep VMs up and running, so "Aggressive restart policy" will restart VM only in certain conditions which are much better described in vSphere Client 7 UI. See the screenshot below.


APD Aggressive restart policy
A VM will be powered off, If HA determines the VM can be restarted on a different host, or if HA cannot detect the resources on other hosts because of network connectivity loss (network partition).

So, what it means? Aggressive restart policy is the same as Conservative but extended for the situation when there is network partitioning. This can be helpful in situations when you have IP storage and experience IP network issues but it does not help in a situation when you have dedicated Fibre Channel SAN and the storage is not available for the whole vSphere Cluster.

We explained to VMware engineering, that there are situations when it is much better to kill all VMs than keep compute (VMs) running without available storage. Based on these discussions, there was created a Feature Request, which was internally named as "super aggressive option" APD. I'm happy to see, that it was implemented and released in vSphere 7 as vSphere advanced option
das.restartVmsWithoutResourceChecks = false (default) / true (super aggressive)
I think this advanced option will be very useful for infrastructure architects / technical designers who will have a good justification to use this advanced option. Here are my typical justifications
  • When the storage subsystem is unavailable for some time, Linux operating system switch file system to Read-Only mode which has a negative impact on running applications. Such a situation typically leads to server restart anyway.
  • When you have an OS/Application clustering solution (for example MSCS) on top of vSphere clustering, having one Application node on one vSphere cluster and another Application node on different vSphere cluster, you prefer to kill VM (App Node) on the problematic cluster (without available storage) to fail-over to App Node (VM) running on the healthy cluster.
Hope this makes sense.

Please leave the comment if you will find this advanced option useful. VMware Engineering might consider adding this option into GUI, based vSphere architects / technical designers' feedback.

References
  • Duncan Epping wrote the blog post about it here.
  • For other "Advanced configuration options for VMware High Availability in vSphere 5.x and 6.x" check VMware KB 2033250.


Friday, May 08, 2020

CPU capacity planning and sizing

During infrastructure capacity planning and sizing, the technical designer has to calculate CPU, RAM, Storage, and Network resource requirements. Recently, I had an interesting discussion with my colleagues on how to estimate CPU requirements for application workload.

Each computer application requires some CPU resources for computational tasks and additional resources for I/O tasks. It is obvious that the computational tasks require CPU cycles, however, it is not so obvious that there are CPU cycles associated also with I/O. In other words, each I/O requires some CPU resources. It does not matter if it is memory, storage, or network I/O.

For example, a generally accepted rule of thumb in the networking is that
1 Hertz of CPU processing is required to send or receive 1 bit/s of TCP/IP.
[Source: VMware vSphere 6.5 Host Resources Deep Dive]

This would mean 2.5Gb/s would require ~ 2.5Ghz CPU, thus ~ 100% of one CPU Core @ 2.5 GHz.

It would be nice to have a similar rule of thumb for storage I/O. I did quick research (googling) but was not able to find any information about CPU requirements for storage I/O.  I did a quick test in my home lab and start the synthetic random workload (4KB I/O) on 4vCPU VM on ESXi host having CPU at 2 GHz, where I was able to see 5,000 IOPS with CPU utilization 8.5%. This would mean one 4KB I/O requires 136 Hz.

4KB I/O on 4x vCPU VM with pCPU @ 2 GHz 
I did another test with 512 B I/O where 1 IOPS requires 114 Hz.
And for 64KB I/O size, 1 IOPS requires 161 Hz.

0.5 KB I/O => 512 Bytes I/O (4,096 bits) = 114 Hz
4 KB I/O => 4,096 Bytes I/O (32,768 bits) = 136 Hz
64 KB I/O => 65,536 Bytes I/O (52,4288 bits) = 161 Hz

Based on my observations, it is difficult to define the rule of thumb for 1 Bit/s or Byte/s but rather I would define CPU (Hz) requirements for 1 storage I/O.

Based on multiple assessments of real datacenter environments, I would say that typical average storage I/O size is around 40-50 KB, therefore here is my rule of thumb
1 Storage I/O requires ~ 150 Hz of CPU processing
This would mean 10,000 IOPS would require ~ 1.5 GHz, thus 60% of one CPU Core @ 2.5 GHz.

Please, be aware that this is a very simplified calculation but clearly shows that storage workload is always associated with CPU requirements and it can help with capacity planning and infrastructure sizing.

What do you think about this calculation?
Do you observe different numbers?
Would you calculate it differently?
You can leave the comment below the article.

Sunday, May 03, 2020

vSphere 7 - Storage Requirements for the vCenter Server Appliance

I have upgraded vSphere in my home lab and realized that VCSA 7.0 storage requirements increased significantly.

Here are the requirements of vCenter Server Appliance 6.7


Here are the requirements of vCenter Server Appliance 7.0


You can see the difference by yourself. VCSA 7.0 requires roughly 30%-60% more storage than VCSA 6.7. It is good to know it especially for home labs where hardware resources are limited or during logical designs of new environments where you do some math calculation to plan hardware requirements.

Monday, April 20, 2020

What's New in vSAN 7

vSAN 7.0 introduces the following new features and enhancements.

vSphere Lifecycle Manager (vLCM).

vLCM enables simplified, consistent lifecycle management for your ESXi hosts. It uses a desired-state model that provides lifecycle management for the hypervisor and the full stack of drivers and firmware. vLCM reduces the effort to monitor compliance for individual components and helps maintain a consistent state for the entire cluster. In vSAN 7.0, this solution supports Dell and HPE ReadyNodes.

Integrated File Services. 

vSAN native File Service delivers the ability to leverage vSAN clusters to create and present NFS (v4.1 and v3) file shares. vSAN File Service extends vSAN capabilities to files, including availability, security, storage efficiency, and operations management.

Native support for NVMe hotplug.

This feature delivers a consistent way of servicing NVMe devices and provides operational efficiency for select OEM drives.

I/O redirect based on capacity imbalance with stretched clusters.

vSAN redirects all VM I/O from a capacity-strained site to the other site, until the capacity is freed up. This feature improves the uptime of your VMs.

Skyline integration with vSphere health and vSAN health. 

Joining forces under the Skyline brand, Skyline Health for vSphere and vSAN are available in the vSphere Client, enabling a native, in-product experience with consistent proactive analytics.

Remove EZT for a shared disk. 

vSAN 7.0 eliminates the prerequisite that shared virtual disks using the multi-writer flag must also use the eager zero thick format.

Support vSAN memory as a metric in performance service. 

vSAN memory usage is now available within the vSphere Client and through the API.

Visibility of vSphere Replication objects in vSAN capacity view. 

vSphere replication objects are visible in vSAN capacity view. Objects are recognized as vSphere replica type, and space usage is accounted for under the Replication category.

Support for large capacity drives. 

Enhancements extend support for 32TB physical capacity drives and extend the logical capacity to 1PB when deduplication and compression are enabled.

Immediate repair after a new witness is deployed. 

When vSAN performs a replacement witness operation, it immediately invokes a repair object operation after the witness has been added.

vSphere with Kubernetes integration. 

CNS is the default storage platform for vSphere with Kubernetes. This integration enables various stateful containerized workloads to be deployed on vSphere with Kubernetes Supervisor and Guest clusters on vSAN, VMFS and NFS datastores.

File-based persistent volumes. 

Kubernetes developers can dynamically create shared (Read/Write/Many) persistent volumes for applications. Multiple pods can share data. vSAN native File Services is the foundation that enables this capability.

vVol support for modern applications. 

You can deploy modern Kubernetes applications to external storage arrays on vSphere using the CNS support added for vVols. vSphere now enables unified management for Persistent Volumes across vSAN, NFS, VMFS, and vVols.

vSAN VCG notification service.

You can subscribe to vSAN HCL components such as vSAN ReadyNode, I/O controller, drives (NVMe, SSD, HDD) and get notified through email about any changes. The changes include firmware, driver, driver type (async/inbox), and so on. You can track the changes over time with new vSAN releases.

Thursday, April 16, 2020

Logical design - storage performance sizing

Storage performance is always a kind of magic because multiple factors come in to play and not all disks are equal, however, in logical design, we have to do some math because capacity (and performance) planning is a very important part of logical design.

How I do it? I do math with some performance assumptions.

Here are assumptions about various disk type performance I use for my capacity planning exercises.

The below numbers are estimated for the random I/O of 64KB I/O size.

Mechanical hard drives
SAS 15k - 200 IOPS
SATA 7k - 80 IOPS

Read Intensive Solid-state disks (SSD)
SATA Read Intensive SSD - 5,000 IOPS (read) / 1,500 IOPS (write)
SAS Read Intensive SSD - 10,000 IOPS (read) / 2,000 IOPS (write)
NVMe Read Intensive SSD - 30,000 IOPS (read) / 2,500 IOPS (write)

Mixed Used Solid-state disks (SSD)
SATA Mixed Used SSD - 5,000 IOPS (read) / 1,800 IOPS (write)
SAS Mixed Used SSD - 12,500 IOPS (read) / 5,000 IOPS (write)
NVMe Mixed Used SSD - 45,000 IOPS (read) / 10,000 IOPS (write)

Write Intensive Solid-state disks (SSD)
SAS Write Intensive SSD - 12,500 IOPS / 7,500 IOPS (write)

SSD assumptions are based on hardware vendors' spec sheets. One of these spec sheets is available here https://www.slideshare.net/davidpasek/dell-power-edge-ssd-performance-specifications

So with these assumptions, the performance math is relatively simple.

Let's have for example 4x SAS Read Intensive SSD within a disk group.
Such a disk group should have the aggregated read performance 4 x 10,000 IOPS = 40,000 IOPS

As we see in the performance numbers above, there is a significant performance difference between SSD read and write.

For our SAS Read Intensive SSD disk we have 10,000 IOPS for 100% read but only 2,000 IOPS for 100% write so we have to normalize these numbers based on expected read/write ratio. If the planned storage workload is 70% read and 30% write, we can assume the single SSD disk will give as 7,000 + 600 IOPS, so in total 7,600 IOPS.

Storage is typically protected by some RAID protection, where the write penalty comes into play. Write penalty is the number of I/O operations required on the backend for a single frontend I/O operation.

Here are write penalties for various RAID protections
RAID 0 (no protection) - write penalty 0
RAID 1 (mirror) - write penalty 2
RAID 5 (erasure coding / single parity) - write penalty 4
RAID 6 (erasure coding / souble parity) - write penalty 6

So, let's calculate the write penalty and write overhead.

If the planned storage workload is 70% read and 30% write and we have total aggregated normalized performance 30,400 IOPS (4 x 7,600) and we have to split the available performance into READ bucket and WRITE bucket.

In our example scenario, we have
READ bucket (70%) - 21,280 IOPS
WRITE bucket (30%) - 9,120 IOPS

Now we have to apply write penalty on write bucket. So let's say we would like to have RAID 5 protection, therefore 9,120 IOPS available on the backend can handle only 2,280 IOPS coming from the frontend.

Based on these calculations, the aggregated performance of RAID 5 protected disk group of 4 Read Intensive SSD disks should be able to handle 23,560 IOPS (21,280 + 2,280) of front-end storage workload.  Please note, that the considered workload pattern is random, 64KB I/O size with Read/Write ratio 70/30.

Do not forget, that this is just logical planning and estimation, every physical system can introduce additional overhead. In real systems, you can have bottlenecks not considered in this simplified calculation. Example of such bottleneck can be
  • storage controller, driver, firmware
  • low queue depth int the storage path (controller, switch, expander, disk), not allowing I/O parallelism
  • network or other bus latency
Therefore, any design should be always tested after implementation and performance results validated with expected numbers.

Are you doing similar design exercises? Any comment or suggestion is always welcome and appreciated.

Saturday, March 21, 2020

What's new in VMware vSphere 7

vSphere 7 has been announced and will be GA and available to download into our labs very soon. Let's briefly summarize what's new in vSphere 7 and put some links to other resources.

vSphere with Kubernetes

Project Pacific evolved into Integrated Kubernetes and Tanzu. vSphere has been transformed in order to support both VMs and containers. Tanzu Kubernetes Grid Service is how customers can run fully compliant and conformant Kubernetes with vSphere. However, when complete conformance with the open-source project isn’t required, the vSphere Pod Service can provide optimized performance and improved security through VM-like isolation. Both of these options are available through VMware Cloud Foundation 4.

The important takeaway is that Kubernetes is now built into vSphere which allows developers to continue using the same industry-standard tools and interfaces they’ve been using to create modern applications. vSphere Admins also benefit because they can help manage the Kubernetes infrastructure using the same tools and skills they have developed around vSphere.

References:
Improved DRS

DRS used to focus on the cluster state and the algorithm would recommend a vMotion when it would benefit the balance of the cluster as a whole. This meant that DRS used to achieve cluster balance by using a cluster-wide standard deviation model. The new DRS logic computes a VM DRS score on the hosts and moves the VM to a host that provides the highest VM DRS score. This means DRS cares less about the ESXi host utilization and prioritizes the VM “happiness”. The VM DRS score is also calculated every minute and this results in a much more granular optimization of resources.


Another new feature is "DRS Scalable Shares". Scalable Shares solves a problem many have been facing over the last decade or so, which is that DRS does not take the number of VMs in the pool into account when it comes to allocating resources.

References:
Refactored vMotions

Improvements in live migrations of monster workloads. Monster VMs with a large memory & CPU footprint, like SAP HANA and Oracle database backends, had challenges being live-migrated using vMotion. The performance impact during the vMotion process and the potentially long stun-time during the switchover phase meant that customers were not comfortable using vMotion for these large workloads. With vSphere 7, we are bringing back that capability as we have greatly improved the vMotion logic.

How the improvement was achieved?
  • Multi-threading
  • A dedicated vCPU is used for page tracing which means that the VM and its applications can keep working while the vMotion processes are occurring. Prior to vSphere 7, page tracing occurred on all vCPUs within a VM, which could cause the VM and its workload to be resource-constrained by the migration itself. 

References:
Assignable Hardware

There is a new framework called Assignable Hardware that was developed to extend support for vSphere features when customers utilize hardware accelerators. It introduces vSphere DRS (for initial placement of a VM in a cluster) and vSphere High Availability (HA) support for VM’s equipped with a passthrough PCIe device or a NVIDIA vGPU. Related to Assignable Hardware is the new Dynamic DirectPath I/O which is a new way of configuring passthrough to expose PCIe devices directly to a VM. The hardware address of a PCIe device is no longer directly mapped to the configuration (vmx) file of a virtual machine. Instead, it is now exposed as a PCIe device capability to the VM.

Together, Dynamic DirectPath I/O, NVIDIA vGPU, and Assignable Hardware are a powerful new combination unlocking some great new functionality. For example, let’s look at a VM that requires an NVIDIA V100 GPU. Assignable Hardware will now interact with DRS when that VM is powered on (initial placement) to find an ESXi host that has such a device available, claim that device, and register the VM to that host. If there is a host failure and vSphere HA kicks in, Assignable Hardware also allows for that VM to be restarted on a suitable host with the required hardware available.


References:
Bitfusion

Bitfusion stays in vSphere 7 as a Tech Preview feature. It allows us to leverage hardware accelerators (GPUs) across an infrastructure (over network fabric) and integrate it with evolving technologies such as FPGAs and custom ASICs using the same infrastructure. This is actually the first implementation of the software-defined composable infrastructure within VMware SDDC stack, therefore it is a very promising and very needed technology for modern applications such as ML/AI workloads.


References:
Precision Time Protocol (PTP)

Precision Time Protocol is helpful for financial and scientific applications requiring sub-millisecond accuracy. PTP requires VM Hardware 17 and it must be enabled on both an in-quest device and an ESXi service. Thus, you have to choose between NTP or PTP.


VM Template Management (Content Library)

VM template check-in and check-out operations with versioning feature. Content Library should also support of controlled replication into remote locations. With these vSphere 7 Content Library improvements, the Content Library is now a mature and very useful tool for VM template management.


References:
vSphere Lifecycle Manager (vLCM)

Desired state of ESXi hosts image (divers & firmware) and host configuration assigned to vSphere Clusters. It requires integration with hardware vendor system management like Dell OMIVV (OpenManage Integration for VMware vCenter) or HPE OneView for VMware vCenter.


References:
vSphere Update Planner

Update Planner is part of vLCM and it monitors current interoperability based on VMware HCL.


References:
vCenter Server Profiles

Export / Import of VCSA (vCenter) configuration. This is good for effective management of a lot of vCenters but please, do NOT expect export/import of vCenter objects like Clusters, VM Folders, Resource Pools, Virtual Switches, etc... This is export / import of VCSA configurations.

References:
VCSA multihoming

VCSA now supports multiple (up to 4) vNICs. The first vNIC (vNIC0) is for management, the second (vNIC1) is dedicated for vCenter Server HA and other vNICs can be used for other purposes like a backup or so.

vCenter and SSO Architecture

vCenter Server Appliance (VCSA) with embedded Platform Service Controler (PSC). External PSC is not supported and it leads into simple SSO topology.

Simplified Certificate Management

Much simpler SSL certificate management. Fewer certificates to manage. For example, vCenter has only two SSL certificates, a Machine SSL certificate, and Certification Authority Certificate. vSphere 7 introduced some vSphere Client UI improvements and also the REST API for certificate management for environments with more vCenters to manage. This is, of course, beneficial for environments implemented based on VMware Validated Designs (VVD) or VMware Cloud Foundation (VCF) environments which is the automated implementation of VVD.


Identity Federation

vCenter is not the key Identity Management System anymore. vSphere Client is using external authentication providers to optimize IDM integration in customer's environments. The first implementation supports only Microsoft Active Directory Federation Services (ADFS), however, VMware SSO still exists, therefore the customer can choose if he will use the brand new Identity Federation or keep existing AD/LDAP authentication through VMware SSO.



vSphere Trust Authority (vTA)

In vSphere 7, vCenter is not trusted authority anymore. vSphere 7 introduces vTA, which creates a hardware root of trust using a separate ESXi host cluster.


vSGX - Support of Intel Software Guard Extensions (SGX)

vSphere 7 introduces support of Intel Software Guard Extensions. I was blogging about SGX a few years ago in blog post Intel Software Guard Extensions (SGX) in VMware VM. Intel SGX allows applications to work with hardware to create a secure enclave that cannot be viewed by the guest OS or hypervisor. With SGX, applications can move sensitive logic and storage into this enclave. SGX is the Intel-only feature. AMD has SEV, which is a different approach.


References:
vSphere 7 Configuration Maximums

Hosts per single vCenter: 2,500
Powered-on VMs on single vCenter: 30,000

Hosts per SSO domain (vCenters in linked mode): 15,000
Powered-on VMs per SSO domain (vCenters in linked mode): 150,000

vCenter Server Latency - vCenter <-> vCenter: 150 ms
vCenter Server Latency - vCenter <-> ESXi: 150 ms
vCenter Server Latency - vSphere Client (web browser) <-> vCenter: 100 ms

The improvements between vSphere 6.7 and 7 are clearly visible in figure below.


For further configuration maximums, look at https://configmax.vmware.com/

Skyline Health for vSphere 7

Skyline Health for vSphere 7 is the unified health check tool for vSphere which works exactly as Skyline Health for vSAN available since vSphere 6.7 U3. It brings into infrastructure operations similar approach developers are doing in agile development methods - automated testing. You can think about it as a set of tests (health check tests) continually testing everything works as expected.


NVMe over Fabric


In vSphere 7, VMware added support for shared NVMe storage using NVMeoF. For external connectivity, NVMe over Fibre Channel and NVMe over RDMA (RoCE v2) are supported.

References:

Conclusion

vSphere 7 is another major vSphere Release. For those who work with VMware virtual infrastructures for ages (see old ESX 3i below), it is amazing where the VMware virtualization platform (vSphere 7, ESXi 7) evolved and what is possible nowadays.

Old good ESXi from Virtual Infrastructure 3 from 2006-ish year :-)
Nowadays, there are totally different reasons to upgrade to the latest vSphere version in comparison to the old days of server consolidation, TCO reduction, and better manageability. Top reasons to upgrade to vSphere 7 are
  • Scalability: The fastest path to the Hybrid/Multi-Cloud and increase scalability through leveraging HCI (Hyper-Converged Infrastructure) 
  • Security: Infrastructure security, secure audits, and account management
  • Performance: maximize performance and efficiency
  • Manageability: Reduce complexity, simplify software patching and hardware upgrades, proactive support technology and services
VMware vSphere 7 new features and incorporation of containers (Kubernetes) into the single platform is another step into VMware's vision to run any app on any cloud. On vSphere 7, you can run
  • monster workloads such as SAP HANA
  • traditional applications in virtual machines
  • modern distributed applications (Cloud Native Applications, CNA) containerized and orchestrated by Kubernetes
This is a great message to all of us, who invested a lot of time (years) to learn, test, design, implement and operate VMware technologies. I can honestly say, ... I LOVE VMWARE ...

Thursday, March 19, 2020

Home Lab 2019/2020

First thing first. Why I have the home lab(s)?

Well, I really need at least one home lab to test and demonstrate VMware vSphere, vSAN, NSX and other components of VMware SDDC stack.

The other reason is, that from time to time I have discussions with other VMware folks discussing our home lab configurations and some of these people have the blog post about their labs. I have never written the blog post about my home lab so far but I realized it is quite useful to document at least some basic information about the lab to quickly show lab details during these discussions and demonstrations. So, here it is.

At the moment, I have two home labs
  1. One in a garage - GARAGE LAB
  2. Second in a flat - APARTMENT LAB
Here are the photos and quick descriptions of my home labs. 

GARAGE LAB




GARAGE LAB vSphere/vSAN Cluster specification
  • 4-node vSphere Cluster (4x ESXi on Dell PE R620) with hybrid vSAN Enabled (4x NVMe 512 GB as cache disks, 8x SATA 500 GB as capacity disks)
  • Each node has 1 CPU Socket (Intel Xeon CPU E5-2620 @ 2.00GHz), 128 Gb RAM, 4x 1Gb Ethernet Port, 1x NVMe 512 GB, 2x SATA 500 GB
GARAGE LAB external storage
  • Flash NAS (NFS) Storage - Synology DS115j , 1x SSD 840 Series 512 GB (465.76 GB SSD)
  • Flash iSCSI Storage - Synology DS115j , 1x SanDisk Ultra II 960 GB (894.3 GB SSD)
  • SATA NAS (NFS) Storage - Synology DS214se, 2x SATA Disk 3TB (2794.52 GB HDD) 
APARTMENT LAB


APARTMENT LAB vSphere/vSAN Cluster specification
  • 4-node vSphere Cluster (4x ESXi on Intel NUC) with All-Flash vSAN Enabled (4x SATA M.2 SSD 180 GB as cache disks, 4x SATA SSD 480 GB as capacity disks)
  • Each node is Intel NUC (6i3SYH) having 1 CPU Socket (Intel Core i3-6100U CPU @ 2.30GHz), 32 GB RAM, 1x 1Gb Ethernet Port, 1x SATA M.2 SSD 180 GB, 1x SATA SSD 480 GB
VMware Licensing

As I'm VMware Certified Design Expert, I'm automatically (after application) awarded as VMware vExpert thus entitled to use VMware vSphere Licenses for almost all VMware products. This is IMHO one of the biggest advantages to be VCDX and/or participate in the VMware vExpert program.