This is a presentation on storage-related changes in VMware vSphere 4.1. I gave this presentation at the Triad VMUG meeting in Greensboro, NC on January 28, 2011.
VMworld 2013: VMware vSphere High Availability - What's New and Best PracticesVMworld
VMworld 2013
Keith Farkas, VMware
Learn more about VMworld and register at http://www.vmworld.com/index.jspa?src=socmed-vmworld-slideshare
Jeff Hunter, VMware
Aventis Systems partnered with Veeam to provide a deep technical dive into the features of Veeam Backup Essentials v9. Check out the recording of the 45-minute live webinar now: https://youtu.be/67prVGb4Dwc
VMworld 2013: VMware vSphere High Availability - What's New and Best PracticesVMworld
VMworld 2013
Keith Farkas, VMware
Learn more about VMworld and register at http://www.vmworld.com/index.jspa?src=socmed-vmworld-slideshare
Jeff Hunter, VMware
Aventis Systems partnered with Veeam to provide a deep technical dive into the features of Veeam Backup Essentials v9. Check out the recording of the 45-minute live webinar now: https://youtu.be/67prVGb4Dwc
Genau an dem Tag, an dem die neue Veeam Availability Suite V9 erschienen ist, konnten wir unser «What's new» Referat durchführen. Somit erhielten die Teilnehmer am 12. Januar brandheisse News zu den neusten Features.
Unser Veeam Certified Trainer Rinon Belegu zeigte an diesem Abend, warum er der Ansicht ist, dass die «Veeam Availability Suite» das beste Produkt für Hochverfügbarkeit in virtuellen Umgebungen ist und den Erfolgskurs mit der Version 9 fortführt.
Diese Features stellte Rinon Belegu vor:
- Veeam integration with EMC Storage Snapshots
- Veeam Cloud Connect Replication
- Primary Storage Integration
- Veeam Explorer™for Oracle and other Explorer enhancements
- Enterprise Enhancements
- Backup Storage Integration
- Scale-out Backup Repository™
VMworld 2015: Site Recovery Manager and Policy Based DR Deep Dive with Engine...VMworld
Policy based management greatly simplifies the work of IT Administrators making it easy to ensure that applications and VMs receive the resources, protection and functionality required. Learn about the latest enhancements of Site Recovery Manager in this space, which represent a huge step towards providing policy based DR. In this session we'll dive deep into how this approach works and how to work with them.
VMworld 2013: vSphere Data Protection 5.5 Advanced VMware Backup and Recovery...VMworld
VMworld Europe 2013
Mauricio Barra, VMware
Learn more about VMworld and register at http://www.vmworld.com/index.jspa?src=socmed-vmworld-slideshare
Jeff Hunter, VMware
Veeam Backup & Replication v8 for VMware — General OverviewVeeam Software
Veeam Backup & Replication is much more than backup – it provides fast, flexible, and reliable recovery of virtualized applications and data. We bring backup and replication together in a single solution to reinvent data protection and deliver the #1 VM backup for VMware vSphere and Hyper-V environments. This poster provides a high-level overview of the architecture of Veeam Backup & Replication running in a VMware environment.
VMware Site Recovery Manager - Architecting a DR Solution - Best Practicesthephuck
This was the slide deck from the Philadelphia VMUG User Conference for the VMware Site Recovery Manager - Architecting a DR Solution session on May 15th, 2014.
Industry leaders Cisco, NetApp, VMware and Symantec have teamed up to develop a best practice framework and performance benchmark based on the VMware vSphere® Storage APIs - Data Protection (VADP). The test configuration uses the popular NetApp FlexPod environment, and the result proves that you can easily protect over 4 TB of virtual machine data per hour. And improved backup performance creates more reliable backups, shorter backup windows and less impact on the vSphere infrastructure.
In this session, we will show how these performance numbers can be easily obtained with minimal hardware and a small budget. In addition to backup performance, we will also discuss restore performance considerations.
Key topics include:
• How to select the correct hardware for the best ROI
• Strategies for minimizing backup impact and maximizing backup throughput
• Performance characteristics of VADP
• SAN or NBD (network) transports: which is recommended?
• Configurations for the fastest possible restores
E’ un’estensione di VMware vCenter che fornisce ai professionisti IT la possibilità di disaster recovery, migrazione di siti e funzionalità di test non distruttive.
VMworld 2013: Protection for All - VMware vSphere Replication & SRM Technical...VMworld
VMworld 2013
Lee Dilworth, VMware
Learn more about VMworld and register at http://www.vmworld.com/index.jspa?src=socmed-vmworld-slideshare
Ken Werneburg, VMware
This is the presentation on VMware integration points, given on October 26, 2010, to the Eastern TN VMUG/EMC User Group at their meeting in Knoxville, TN.
Genau an dem Tag, an dem die neue Veeam Availability Suite V9 erschienen ist, konnten wir unser «What's new» Referat durchführen. Somit erhielten die Teilnehmer am 12. Januar brandheisse News zu den neusten Features.
Unser Veeam Certified Trainer Rinon Belegu zeigte an diesem Abend, warum er der Ansicht ist, dass die «Veeam Availability Suite» das beste Produkt für Hochverfügbarkeit in virtuellen Umgebungen ist und den Erfolgskurs mit der Version 9 fortführt.
Diese Features stellte Rinon Belegu vor:
- Veeam integration with EMC Storage Snapshots
- Veeam Cloud Connect Replication
- Primary Storage Integration
- Veeam Explorer™for Oracle and other Explorer enhancements
- Enterprise Enhancements
- Backup Storage Integration
- Scale-out Backup Repository™
VMworld 2015: Site Recovery Manager and Policy Based DR Deep Dive with Engine...VMworld
Policy based management greatly simplifies the work of IT Administrators making it easy to ensure that applications and VMs receive the resources, protection and functionality required. Learn about the latest enhancements of Site Recovery Manager in this space, which represent a huge step towards providing policy based DR. In this session we'll dive deep into how this approach works and how to work with them.
VMworld 2013: vSphere Data Protection 5.5 Advanced VMware Backup and Recovery...VMworld
VMworld Europe 2013
Mauricio Barra, VMware
Learn more about VMworld and register at http://www.vmworld.com/index.jspa?src=socmed-vmworld-slideshare
Jeff Hunter, VMware
Veeam Backup & Replication v8 for VMware — General OverviewVeeam Software
Veeam Backup & Replication is much more than backup – it provides fast, flexible, and reliable recovery of virtualized applications and data. We bring backup and replication together in a single solution to reinvent data protection and deliver the #1 VM backup for VMware vSphere and Hyper-V environments. This poster provides a high-level overview of the architecture of Veeam Backup & Replication running in a VMware environment.
VMware Site Recovery Manager - Architecting a DR Solution - Best Practicesthephuck
This was the slide deck from the Philadelphia VMUG User Conference for the VMware Site Recovery Manager - Architecting a DR Solution session on May 15th, 2014.
Industry leaders Cisco, NetApp, VMware and Symantec have teamed up to develop a best practice framework and performance benchmark based on the VMware vSphere® Storage APIs - Data Protection (VADP). The test configuration uses the popular NetApp FlexPod environment, and the result proves that you can easily protect over 4 TB of virtual machine data per hour. And improved backup performance creates more reliable backups, shorter backup windows and less impact on the vSphere infrastructure.
In this session, we will show how these performance numbers can be easily obtained with minimal hardware and a small budget. In addition to backup performance, we will also discuss restore performance considerations.
Key topics include:
• How to select the correct hardware for the best ROI
• Strategies for minimizing backup impact and maximizing backup throughput
• Performance characteristics of VADP
• SAN or NBD (network) transports: which is recommended?
• Configurations for the fastest possible restores
E’ un’estensione di VMware vCenter che fornisce ai professionisti IT la possibilità di disaster recovery, migrazione di siti e funzionalità di test non distruttive.
VMworld 2013: Protection for All - VMware vSphere Replication & SRM Technical...VMworld
VMworld 2013
Lee Dilworth, VMware
Learn more about VMworld and register at http://www.vmworld.com/index.jspa?src=socmed-vmworld-slideshare
Ken Werneburg, VMware
This is the presentation on VMware integration points, given on October 26, 2010, to the Eastern TN VMUG/EMC User Group at their meeting in Knoxville, TN.
VMware vSphere Version Comparison 4.0 to 6.5Sabir Hussain
VMware vSphere leverages the power of virtualization to transform datacenters into simplified cloud computing infrastructures and enables IT organizations to deliver flexible and reliable IT services VMware vSphere virtualizes and aggregates the underlying physical hardware resources across multiple system and provides pools off virtual resources to the datacenter.
VM Virtualization
VMGate.com
The Storage for Virtual Environments seminar focuses on the challenges of backup and recovery in a virtual infrastructure, the various solutions that users are now using to solve those challenges, and a roadmap for making the most of all an organization’s virtualization initiatives.
This slide deck was used by Stephen Foskett for his
Upgrading your Private Cloud to Windows Server 2012 R2Tudor Damian
Learn about the functionality and processes that are available to enable you to move your private cloud deployments to Windows Server 2012 R2 with zero downtime. Understand the options that are available to you and the considerations that need to be made as you determine the best path for continuing to keep your environment on the best technology available for private clouds today. This session covers the end to end approach including Hyper-V, Clustering, Storage and SCVMM.
Where We're Headed and Where NSX Fits InScott Lowe
In this presentation, I take a look at some broad industry trends and how they are driving the need for a network virtualization solution such as VMware NSX.
This presentation provides an introductory overview of Linux networking options, including network namespaces, VLAN interfaces, MACVLAN interfaces, and virtual Ethernet (veth) interfaces.
Why is it that cloud computing operational models haven't taken hold more fully in enterprise IT? In this presentation, I'll explore the reasons I think are behind the problem, and what can be done to address these reasons.
The Vision for the Future of Network Virtualization with VMware NSXScott Lowe
This presentation recaps some announcements and demonstrations made at VMworld 2015 regarding new features and new functionality tentatively anticipated for future versions of VMware NSX.
The theme for the 2015 LabMan Conference (held at UNT in Denton, TX) is sustainability, and this closing keynote presentation talks about sustaining your career.
This presentation, given at the Nashville VMUG Converge 2015 event on April 8, 2015, provides an overview of Vagrant and Docker as tools that VMware administrators might find useful.
This presentation was presented at various VMUG user conferences (Dallas, Chicago, Phoenix, SoCal) in September 2014, and discusses how VMware administrators can close the "cloud skills gap" to stay technically relevant in a fast-changing industry.
The Future of Cloud Networking is VMware NSX (Danish VMUG edition)Scott Lowe
This presentation provides a definition of cloud computing (using NIST SP800-145), then builds on that definition to show why cloud networking has specific needs and how VMware NSX was built to meet those needs.
The Future of Cloud Networking is VMware NSXScott Lowe
This presentation was first given at Varrow Madness 2014 and discusses the need for a solution specifically designed (like VMware NSX) for cloud networking
This presentation is an update to a presentation from October 2012 titled "Three Technologies Worth Watching or Learning," and was first presented in Sydney, Australia, in February 2014.
SDN, Network Virtualization, and the Right AbstractionScott Lowe
This presentation, given at the 2013 Indianapolis VMware User Conference on July 25, discusses the relationship between SDN and network virtualization, and highlights the value of the right abstraction in network virtualization.
5 Thoughts for Staying Sharp and Relevant (Boston)Scott Lowe
This presentation, given at the Boston VMUG in June 2013, contains some thoughts and ideas about assimilating and managing information within the context of keeping up with today's fast-moving IT industry.
This presentation was given at the Carolinas Regional VMUG in June 2013. It discusses the key components and technologies involved in building a network virtualization solution.
Transcript: Selling digital books in 2024: Insights from industry leaders - T...BookNet Canada
The publishing industry has been selling digital audiobooks and ebooks for over a decade and has found its groove. What’s changed? What has stayed the same? Where do we go from here? Join a group of leading sales peers from across the industry for a conversation about the lessons learned since the popularization of digital books, best practices, digital book supply chain management, and more.
Link to video recording: https://bnctechforum.ca/sessions/selling-digital-books-in-2024-insights-from-industry-leaders/
Presented by BookNet Canada on May 28, 2024, with support from the Department of Canadian Heritage.
Essentials of Automations: Optimizing FME Workflows with ParametersSafe Software
Are you looking to streamline your workflows and boost your projects’ efficiency? Do you find yourself searching for ways to add flexibility and control over your FME workflows? If so, you’re in the right place.
Join us for an insightful dive into the world of FME parameters, a critical element in optimizing workflow efficiency. This webinar marks the beginning of our three-part “Essentials of Automation” series. This first webinar is designed to equip you with the knowledge and skills to utilize parameters effectively: enhancing the flexibility, maintainability, and user control of your FME projects.
Here’s what you’ll gain:
- Essentials of FME Parameters: Understand the pivotal role of parameters, including Reader/Writer, Transformer, User, and FME Flow categories. Discover how they are the key to unlocking automation and optimization within your workflows.
- Practical Applications in FME Form: Delve into key user parameter types including choice, connections, and file URLs. Allow users to control how a workflow runs, making your workflows more reusable. Learn to import values and deliver the best user experience for your workflows while enhancing accuracy.
- Optimization Strategies in FME Flow: Explore the creation and strategic deployment of parameters in FME Flow, including the use of deployment and geometry parameters, to maximize workflow efficiency.
- Pro Tips for Success: Gain insights on parameterizing connections and leveraging new features like Conditional Visibility for clarity and simplicity.
We’ll wrap up with a glimpse into future webinars, followed by a Q&A session to address your specific questions surrounding this topic.
Don’t miss this opportunity to elevate your FME expertise and drive your projects to new heights of efficiency.
The Art of the Pitch: WordPress Relationships and SalesLaura Byrne
Clients don’t know what they don’t know. What web solutions are right for them? How does WordPress come into the picture? How do you make sure you understand scope and timeline? What do you do if sometime changes?
All these questions and more will be explored as we talk about matching clients’ needs with what your agency offers without pulling teeth or pulling your hair out. Practical tips, and strategies for successful relationship building that leads to closing the deal.
Accelerate your Kubernetes clusters with Varnish CachingThijs Feryn
A presentation about the usage and availability of Varnish on Kubernetes. This talk explores the capabilities of Varnish caching and shows how to use the Varnish Helm chart to deploy it to Kubernetes.
This presentation was delivered at K8SUG Singapore. See https://feryn.eu/presentations/accelerate-your-kubernetes-clusters-with-varnish-caching-k8sug-singapore-28-2024 for more details.
Smart TV Buyer Insights Survey 2024 by 91mobiles.pdf91mobiles
91mobiles recently conducted a Smart TV Buyer Insights Survey in which we asked over 3,000 respondents about the TV they own, aspects they look at on a new TV, and their TV buying preferences.
GDG Cloud Southlake #33: Boule & Rebala: Effective AppSec in SDLC using Deplo...James Anderson
Effective Application Security in Software Delivery lifecycle using Deployment Firewall and DBOM
The modern software delivery process (or the CI/CD process) includes many tools, distributed teams, open-source code, and cloud platforms. Constant focus on speed to release software to market, along with the traditional slow and manual security checks has caused gaps in continuous security as an important piece in the software supply chain. Today organizations feel more susceptible to external and internal cyber threats due to the vast attack surface in their applications supply chain and the lack of end-to-end governance and risk management.
The software team must secure its software delivery process to avoid vulnerability and security breaches. This needs to be achieved with existing tool chains and without extensive rework of the delivery processes. This talk will present strategies and techniques for providing visibility into the true risk of the existing vulnerabilities, preventing the introduction of security issues in the software, resolving vulnerabilities in production environments quickly, and capturing the deployment bill of materials (DBOM).
Speakers:
Bob Boule
Robert Boule is a technology enthusiast with PASSION for technology and making things work along with a knack for helping others understand how things work. He comes with around 20 years of solution engineering experience in application security, software continuous delivery, and SaaS platforms. He is known for his dynamic presentations in CI/CD and application security integrated in software delivery lifecycle.
Gopinath Rebala
Gopinath Rebala is the CTO of OpsMx, where he has overall responsibility for the machine learning and data processing architectures for Secure Software Delivery. Gopi also has a strong connection with our customers, leading design and architecture for strategic implementations. Gopi is a frequent speaker and well-known leader in continuous delivery and integrating security into software delivery.
Kubernetes & AI - Beauty and the Beast !?! @KCD Istanbul 2024Tobias Schneck
As AI technology is pushing into IT I was wondering myself, as an “infrastructure container kubernetes guy”, how get this fancy AI technology get managed from an infrastructure operational view? Is it possible to apply our lovely cloud native principals as well? What benefit’s both technologies could bring to each other?
Let me take this questions and provide you a short journey through existing deployment models and use cases for AI software. On practical examples, we discuss what cloud/on-premise strategy we may need for applying it to our own infrastructure to get it to work from an enterprise perspective. I want to give an overview about infrastructure requirements and technologies, what could be beneficial or limiting your AI use cases in an enterprise environment. An interactive Demo will give you some insides, what approaches I got already working for real.
Kubernetes & AI - Beauty and the Beast !?! @KCD Istanbul 2024
Storage Changes in VMware vSphere 4.1
1. Storage Changes in VMware vSphere 4.1 A quick review of changes and new features Scott Lowe, VCDX 39 vSpecialist, EMC Corporation Author, Mastering VMware vSphere 4 Blogger, http://blog.scottlowe.org
2. Storage Feature Summary 8 Gbps FC HBA and expanded support for FCoE CNAs New storage performance statistics Storage I/O Control vStorage APIs for Array Integration iSCSI enhancements
3. New Storage Performance Statistics More comprehensive performance statistics available both in vCenter and esxtop/resxtop Historical/real-time via GUI in vCEnter Real-time via esxtop/resxtop for drill-down/scripting Latency and throughput statistics available for: Datastore per host Storage adapter and path per host Datastore per VM VMDK per VM Greater feature parity across all storage protocols
5. The I/O Sharing Problem What You See Now What You Should See MicrosoftExchange MicrosoftExchange online store online store data mining data mining datastore datastore
6. Solution: Storage I/O Control (SIOC) CPU shares: Low Memory shares: Low CPU shares: High Memory shares: High CPU shares: High Memory shares: High I/O shares: High I/O shares: Low I/O shares: High 32GHz 16GB MicrosoftExchange online store data mining Datastore A
10. Allocate I/O Resources Shares translate into ESX I/O queue slots VMs with more shares are allowed to send more I/O’s at a time Slot assignment is dynamic, based on VM shares and current load Total # of slots available is dynamic, based on level of congestion data mining MicrosoftExchange online store I/O’s in flight STORAGE ARRAY
11. Congestion Triggers SIOC Congestion signal: ESX-array response time > threshold Default threshold: 30ms Should set different defaults for SSD and SATA Changing default threshold (not usually recommended) Low latency goal: set lower if latency is critical for some VMs High throughput goal: set close to IOPS maximization point
13. Storage Integration Points VI Client VM ESX Storage Stack VMFS NFS Snap request SvMotion request VM provisioning cmd Turn thin prov on/off VSS via VMware Tools NFS client VMware LVM Co-op vStorage API for Data Protection (VDDK) Datamover Co-op vCenter SRM Vendor-specific Plug-In e.g. EMC Virtual Storage Integrator Network Stack vStorageAPI for Multi- pathing NMP View VMware-to-Storage relationships Provision datastores more easily Leverage array features (compress/dedupe, file/filesystem/LUN snapshots HBA Drivers NIC Drivers FC/FCoE & iSCSI NFS Array APIs/Mgmt Vendor Specific vStorage API for SRM VM-Aware Unisphere VAAI SCSI cmds Storage Array Vendor-specific VAAI SCSI command support Future NFS offloads
14. Current VAAI Primitives Hardware-Accelerated Locking = 10-100x better metadata scaling Replace LUN locking with extent-based locks for better granularity Reduce number of “lock” operations required by using one efficient SCSI command to perform pre-lock, lock, and post-lock operations Increases locking efficiency by an order of magnitude Hardware-Accelerated Zero = 2-10x lower number of IO operations Eliminate redundant and repetitive host-based write commands with optimized internal array commands Hardware-Accelerated Copy = 2-10x better data movement Leverage native array Copy capability to move blocks
15. Hardware-Accelerated Locking Without API Reserves the complete LUN so that it could obtain a lock Required several SCSI commands LUN level locks affect adjacent hosts With API Locks occur at a block level One efficient SCSI command - SCSI Compare and Swap (CAS) Block level locks have no effect on adjacent hosts. Use Cases Bigger clusters with more VMs View, Lab Manager, Project Redwood More & Faster VM Snapshotting
17. Hardware-Accelerated Zero Without API SCSI Write - Many identical small blocks of zeroes moved from host to array for MANY VMware IO operations Extra zeros can be removed by EMC arrays after the fact by “zero reclaim” New Guest IO to VMDK is “pre-zeroed” With API SCSI Write Same - One giant block of zeroes moved from host to array and repeatedly written Thin provisioned array skips zero completely (pre “zero reclaim”) Use Cases Reduced IO when writing to new blocks in the VMDK for any VM Time to create VMs (particularly FT-enabled VMs SCSI WRITE (0000…..) SCSI WRITE (data) SCSI WRITE (0000….) SCSI WRITE (data) Repeat MANY times… SCSI WRITE SAME (0 * times) SCSI WRITE (data) VMDK
19. Hardware-Accelerated Copy “let’s Storage VMotion” “let’s Storage VMotion” Without API SCSI Read (Data moved from array to host) SCSI Write (Data moved from host to array) Repeat Huge periods of large VMFS level IO, done via millions of small block operations With API SCSI Extended Copy (Data moved within array) Repeat Order of magnitude reduction in IO operations Order of magnitude reduction in array IOps Use Cases Storage VMotion VM Creation from Template SCSI WRITE SCSI WRITE SCSI WRITE ..MANY times… SCSI READ SCSI READ SCSI READ ..MANY times… SCSI EXTENDED COPY “Give me a VM clone/deploy from template”
22. iSCSI Enhancements in vSphere 4.1 Boot from software iSCSI (iBFT) iSCSI offloading iSCSI session management Additions have also been made to the CLI
23. Steps in Booting from Software iSCSI Ensure that the NIC you wish to use supports iSCSI Boot. Ensure that the NIC has a supported version of firmware. Ensure that iSCSI Boot option is selected in the host BIOS for the NIC. Configure the iSCSI Boot parameters in the NIC BIOS. Configure the iSCSI target to allow initiator (NIC) access. Configure a LUN on the iSCSI target and present to the initiator.
The problem Storage I/O control is addressing is the situation where some less important workloads are taking the majority of I/O bandwidth from more important applications. In the case of the three applications shown here, the data mining is hogging a majority of the storage I/O resource. And the two more important to the business operations are getting less performance than needed. <Click> what one wants to see is a distribution of I/O that is aligned with the importance of each virtual machine. Where the most important business critical applications are getting the I/O bandwidth needed for them to be responsive and the less critical data mining application is taking less I/O bandwidth.
I/O shares can be set at the Virtual Machine level and although this capability has been there for a few previous releases, it was not enforced on a VMware cluster wide level until release 4.1. Prior to 4.1 the I/O shares and limits were enforced for a VM with more than one virtual disk or a number of VMs on a single ESX server. <click> But with 4.1 these I/O shares are now used to distribute I/O bandwidth across all the ESX servers which have access to that shared datastore.
The ability to set shares for I/O is done via edit properties on the virtual machine. This screen shows two virtual disks and the ability to set priority and limits on the I/Os per second.
Once the shares are set on the virtual machines in a vmware cluster, one needs to also enable the “Storage I/O Control” option on the properties screen for that datastores on which you want to have Storage I/O control working. The other thing that is needed for Storage I/O to kick in is that congestion measured in the form of latency must exist for a period of time on the datastore before the I/O control kicks in. The example which comes to mind is a car pool lane is not typically enforced when there is not a lot of traffic on the highway. It would be of limited value if you could travel at the same speed in the non car pool lane as well as the car pool lane. In much the same way, Storage I/O control will not be put into action when there is latency below a sustained value of 30 msec.
One can then observe which VMs have what shares and limits set via the virtual machine tab for the datastore. As datastores are now objects managed by vCenter, there are several new views in vSphere that enable you see which ESX Servers are connected to a datastore and which VMs are sharing that datastore. Many of these views also allow one to customize which columns are displayed and create specific views to report on usage.
The way in which these I/O shares are used to effect performance is that queue depth for each ESX server can be assigned and throttled to align the specific shares assigned for each VM running on the collective pool of storage. In the case of our 3 VMs displayed earlier, we have the data mining vm getting the least number of queues assigned while the other two VMs are getting many more queuing slots enabled for their I/O.
It is important to understand that SIOC does not kick in until the congestion of the datastore gets above the threshold of 35 ms for a period of time. It is a weighted average that is used to determine this latency is not just a minor spike that comes and goes quickly. This threshold value can be modified but should be done only with great care and consideration as if its too low, it might be on and off again a lot or if too high might not kick in at all.